As Tim Hudak prepared for his second and final shot at becoming Ontario's premier, the word went out through Conservative circles in the nation's capital: Do not help this man.

Mr. Hudak, then the leader of the provincial Progressive Conservatives, was a kindred spirit set to run on a right-wing agenda. He had a decent shot at knocking off a Liberal incumbent with whom Stephen Harper had a frosty relationship. And after more than a decade in the political wilderness, his Tories badly needed organizational support from federal cousins who had recently been in the business of winning.

Before Mr. Hudak's first election leading his party, in 2011, such support was forthcoming. The federal Conservatives lent experienced campaign managers for target ridings, shared their volunteer lists, and helped raise money. They even let the provincial Tories use a campaign bus.

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But on the final day of that election campaign, before the votes were even counted, Mr. Hudak made a bad mistake that went a long way toward souring his relationship with the federal party: He fired his chief of staff, Lynette Corbett.

Mixed views about whether Ms. Corbett deserved to be let go, after a behind-the-scenes power struggle among Mr. Hudak's senior officials, are beside the point.

What matters is that she's among the very best friends of Jenni Byrne.

There are only a few backroom operators in this country whose bad side needs to be avoided at all costs. And Ms. Byrne – the Prime Minister's campaign manager, his enforcer, his primary connection to his party's grassroots, and one of his longest-serving loyalists – is most emphatically one of them.

"Pretty much from the day Lynette was fired, we couldn't get a phone call returned," recalls a senior member of Mr. Hudak's campaign team. "It pretty quickly became clear this wasn't an issue to be managed. It was a fact to be accepted."

Never mind central support; all but the bravest federal Conservatives were reluctant even to be seen at a Hudak fundraiser, for fear of what it would do to their careers.

It is unclear whether Mr. Harper was fully aware that his party was choking off resources to Mr. Hudak; if he was, he didn't much care. Such is the leeway afforded to the woman who claimed credit for steering the Prime Minister to majority government, and whom he will be counting on to help him hold on to it in this year's federal campaign.

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Ms. Byrne's story is a remarkable one, in part because her ascent has been so improbable. In political backrooms that continue to be dominated by middle-aged men with advanced degrees, a young woman from small-town, blue-collar Eastern Ontario, who left nursing school without graduating, has become the ultimate alpha.

It is all the more so because, rarely seen in public, and rebuffing any and all media requests, she has become the closest thing official Ottawa has to an urban legend.

Trying to puncture the air of mystery she has cultivated – to figure out how she attained power, how much of it she really has, and how she wields it – can be confounding.

She did not make herself available for this story, although she did allow several people close to her to talk, and in some cases to respond to criticisms of her. Of the roughly 30 sources who were interviewed – among them, friends and rivals, current and former colleagues, cabinet ministers and senior campaign officials – most were willing to speak only on a not-for-attribution basis, reflecting the culture she has helped to create. And depending on their personal experience with her, and whether they are on her good side or bad, they often contradicted each other about everything from her temperament to her skill set to her relationship with the Prime Minister.

Still, there are a few accepted truths. She is willing to do what Mr. Harper asks of her. She is especially good at "issues management," which means making messes go away. She is valued for her ability to make quick decisions and stick with them, rare for a political operative. She is rarer still for not having blown herself up with one of those. She does not mind playing the bad cop, and might even enjoy it. She is not terribly interested in policy, but presents herself as deeply in touch with the Conservative base, and speaks on its behalf in the corridors of power.

From these, and even from the contradictions, emerges a picture of her impact on the governing Conservatives – their daily agenda and messaging, their rigid commitment to discipline, their internal divisions, their strengths and weaknesses heading into the coming campaign, and their uncertain future beyond that.

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Jim Armour, a former communications director for Mr. Harper, suggested that the challenge of this story is "separating myth from reality, and separating Jenni Byrne from Stephen Harper."

But when it comes to Mr. Harper, and Ms. Byrne, and the party she has helped him build, it all gets a bit inseparable.

Staying true to her roots

There is a photo that Ms. Byrne has been known to pull out during high-level meetings and pass around. It shows a little girl proudly standing alongside her father, over a dead deer he has just shot. Her point is that these are the sorts of people who tend not to be seen or heard within the Ottawa bubble, but who need to be top-of-mind for Conservatives. And that, as the girl in the photo, she speaks for them.

"If you want to understand anything about her, you have to understand where she comes from," says Employment and Social Development Minister Pierre Poilievre, whom she dated from her early days in Ottawa until 2011.

It has been about two decades since Ms. Byrne, now 38, left Fenelon Falls, where she grew up. But the Eastern Ontario town of about 1,800 people – the kind of conservative bedrock where guns are good, soldiers are revered, government is viewed with suspicion, and criminals are seen as in need of severe punishment – still very much defines her.

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So, too, does her upbringing. Ms. Byrne was very close to her mother, a teacher named Julie who died in 2010 at just 58. But her father, Jerry, was her entry point into politics. A self-employed carpenter who grew up with 10 siblings, he joined the Reform Party in the mid-1990s in protest against the governing Liberals' new gun registry, and his teenaged daughter quickly followed suit.

The perspective with which she came to Ottawa after leaving her hometown will be instantly familiar to those who have witnessed the current government's rigid commitment to certain articles of faith for its base – in some measure because of Ms. Byrne's influence.

She is not, by any stretch, a wonk. Her specialty is operations – making things run properly, and holding people to account – and she has little interest in long policy debates. But during stints in the Prime Minister's Office, as issues-management director and a deputy chief of staff, she has helped to shape daily messaging. In recent years, even when working for the Conservative Party rather than the government, she has usually gone to the morning meeting between Mr. Harper and his senior staff. The PM sometimes turns to her for a gut check, and even when he doesn't, she often inserts herself into the debate.

"Part of her thing is a constant sobriety check," says Yaroslav Baran, a former communications officer for Mr. Harper, who worked with Ms. Byrne. "What are they talking about at the Tim Hortons in Fenelon Falls?"

Asked what issues she may have influenced, several government insiders cited the Omar Khadr file. When the complexities of the former prisoner's legal case led to any equivocating about whether the government should be trying to keep him out of the country or behind bars, she would do her best to shut it down. To the base, he was a terrorist who merited not a shred of sympathy.

As with other causes on which she has been particularly vocal, among them eliminating the gun registry and keeping marijuana possession criminalized, she may have been preaching to the choir. But she manages, at least, to reinforce Mr. Harper's instincts. She has also tried to fight the tendency – a risk for any party in power – to be steered toward the political centre or made technocratic by the machinery of government.

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Former foreign affairs minister John Baird, who was not shy about offering what he calls a "robust challenge" to his department's officials, notes that some ministers are less inclined to push back against bureaucrats telling them how things have to be done. When Ms. Byrne felt that compromised the government's priorities or was at odds with public expectations, says Mr. Baird, she would intervene.

At times, she has even argued against putting much public focus on issues Mr. Harper himself is actively pursuing. "She hated trade agreements," recalls a former staffer in the Prime Minister's Office. "Not that she didn't think the government should be doing them. Just, 'Don't overestimate it, nobody outside Ottawa gives a shit.'"

Beyond citing her roots, Ms. Byrne's credibility on these fronts rests with her being the rare political operative at her level willing to get her hands dirty on the ground. "What I love about her most is she'll be there for the high-level meetings, but she'll also go door-to-door with me," says Veteran Affairs Minister Erin O'Toole, with whom she is friends.

Not all Conservatives are quite as sold. To some, her claim to speak for those outside Ottawa looks like a shtick. They roll their eyes at what they see as her efforts to prove she walks the talk, such as her going on a seal hunt in Newfoundland. (Her Facebook profile includes a rather graphic photo from that trip.) They suggest she sometimes conflates her pet issues with Mr. Harper's best interests. And they complain that her influence sometimes has less to do with her expertise than with her loudness.

"Her approach to argument," another former PMO staffer said, "is blitzkrieg."

But then, her aggressiveness is a big part of what got her a seat at the table in the first place – because it is absolutely essential to the primary role she plays for Mr. Harper, which has less to do with life back in Fenelon Falls than with political realities she discovered shortly after leaving it.

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A party defined by discipline...

"If you surveyed ministers' offices about what it's like when Jenni Byrne calls you," says one of the former PMO staffers, "it's probably 'butt-clenching time.'"

Most political parties have enforcers. Few have approached that role as ferociously as has Ms. Byrne.

In part, it is a matter of personality. Even as a child, she was strong-willed. She has always had a temper; those who encountered her in politics when she was barely in her 20s say she was rarely afraid of whom she might offend.

Some Conservatives wonder aloud if negative reactions to her reflect a sexist double standard. Being yelled at or threatened or disciplined by senior staff, even getting caught in nasty turf battles with them, has long been one of the pleasures of working in politics; it just usually hasn't been a young woman dishing it out.

"When it's a man in that role, those qualities tend to be seen as 'decisive,' 'no-nonsense,' 'suffering no fools,'" says Mr. Baran, who acknowledges that he and Ms. Byrne didn't always see eye to eye when working together. "When it's a woman, those qualities somehow take on a more nasty and personal tone."

Still, she has helped to instill a culture of fear throughout her party that can be traced to the insights she gleaned about the conservative movement in her early years in politics, and an almost pathological determination she shares with the Prime Minister to avoid returning to the bad old days.

After more than nine years in office, the Conservatives' staffing ranks are filled largely with people who have never known anything other than being in government. Then there is Ms. Byrne, who started at the bottom of the pecking order in a party that no longer exists.

In 1997, when she was studying nursing at Georgian College in Barrie, Ont., she volunteered for the Reform Party's federal campaign. Her reward was to ride around Ontario on a bus with a bunch of other right-wing kids, having abuse hurled at them: "Racist, sexist, anti-gay, Preston Manning go away!"

Kory Teneycke, the long-time backroom operative who has rejoined the Conservative campaign team after serving as a Sun News executive, first got to know Ms. Byrne back then; he, too, was riding that bus, as was Ray Novak, who is now the PM's chief of staff. "The sunnier side of her personality was probably a little more dominant," Mr. Teneycke recalls. "But the toughness was already there."

That toughness would be needed in the years that followed, when Ms. Byrne would be involved in all the tortuous efforts to fashion a right-of-centre alternative palatable to voters. Working her way up from a Reform internship in Ottawa and a stint as the party's deputy youth director, she was in the party's Calgary headquarters as it transitioned to the Canadian Alliance and endured the tumult of the Stockwell Day years and then his ouster in favour of Mr. Harper.

She would earn Mr. Harper's trust by backing him early in the contest to lead the newly merged Conservative Party, when former Ontario Premier Mike Harris (who ultimately decided not to run) was the presumptive front runner, and then fighting for the future PM with her elbows out amid fears that Belinda Stronach's deep pockets would give her the edge.

If there was a constant during all this chaos, it was that discipline – or a lack thereof – kept costing the parties for which Ms. Byrne was toiling, as the Liberals kept besting them. Although the newly merged party had started to get its act together by the 2004 campaign, during which she worked on its Ontario desk, a series of screw-ups showed it still wasn't quite ready for prime time. Bozo eruptions by candidates, Mr. Harper himself veering off script, some shaky resource planning, and general unpreparedness for the scrutiny that came with being close to power – all helped snatch defeat from the jaws of victory.

The reaction to that defeat was both swift and lasting. The Conservatives would prize discipline above almost all else; their political culture would become almost militaristic in nature. And nobody other than Mr. Harper himself would be more responsible for it than Ms. Byrne.

Starting with the preparations for the 2006 election, by which point she was the Conservatives' deputy national campaign manager, her responsibilities included making sure candidates wouldn't cause embarrassment. That meant vetting them, training them, heading off any controversies they might get themselves into, and putting the fear of God into them about making mistakes in the first place.

It was a task to which Ms. Byrne, whom Mr. Teneycke describes as "able to out-interrogate a Mossad agent," would prove ideally suited. And she would continue to carry it out once those candidates were elected.

When working in government, she expects caucus members and staffers to be rigorously prepared, and can be merciless when they're not. Although she is not known to veer into personal insults, the tone, as one former colleague put it, is "Prove to me you're not incompetent." It is much the same in her dealings with party staff in Ottawa, and with organizers across the country.

Ms. Byrne yells a lot, but that's only a part of what makes her intimidating. Because she has the PM's ear, and strong influence over personnel decisions, it is well known that getting on her bad side can be a career killer.

Although she tends to go easier on them than she does on staffers and backbenchers, she has helped to create an atmosphere in which even relatively senior ministers appear terrified of venturing from their tightly scripted talking points. Beyond creating a recognition of the need for professionalization, what happened in 2004 and the campaigns before left some Conservatives with discomfort verging on paranoia toward both mainstream media and an Ottawa establishment they believe is waiting to pounce on their every minor mistake.

Acting on or extrapolating from Mr. Harper's wishes, Ms. Byrne has spent a lot of time making sure everyone else shares this attitude, helping to create a culture in which, behind the scenes, she has pushed back hard against attempts by communications staff to do what communications staff normally do, which is engage with reporters. And she has let it be known that she expects other Conservatives to share her aversion to working official Ottawa's social scene, and that she is keeping tabs on who's spending too much time at Hy's Steakhouse or at cocktail parties thrown by lobbyists.

Sustaining this culture has been an accomplishment. After this long in power, many governments become comfortable and bloated, taking their success for granted. The Conservatives have kept a certain oppositional mentality, never forgetting where they came from.

There has been some downside, as well. To some extent, the Conservatives' toxic relationship with the media has become a self-fulfilling prophecy. And attracting and retaining good staff has proved at times to be a challenge: As one party veteran put it, "We're not winning any Best Employer in Canada awards."

On that note, for all that the Conservatives continue to put forward a united front, there are some serious behind-the-scenes fault lines.

... But also a party divided

When Conservatives gathered at the Canadian War Museum in October, 2012, to roast Doug Finley, the ailing businessman turned senator who had managed Mr. Harper's 2006 and 2008 election campaigns, they witnessed the rarest of sights: Jenni Byrne speaking in public.

Ms. Byrne's friends tend to bring up how proud of her they were that night: Even though she was nervous about being out of her comfort zone, as anyone who normally keeps a low profile would be about roasting a former mentor, she rose to the occasion with a funny and charming performance that, they say, showed what she is really like beyond the mythology.

Some of Mr. Finley's old friends offer a different take: They say that while her fellow speakers good-naturedly poked fun at such accepted topics as his grumpiness and heavy drinking, Ms. Byrne tried to score points for her own legacy and against his. Among the takeaways from her speech, by these accounts, was that she had succeeded where he failed by managing the Conservatives to a majority government; that she had managed to do so without running into ethical problems the way his campaigns had; and that, when she was his deputy, she had been doing most of the heavy lifting anyway. Mr. Finley wasn't easy to offend, they say, but that night he was hurt.

There is no way of knowing for sure how Mr. Finley, who died of cancer a few months later, really felt. But the mixed reviews, the better part of three years after the fact, speak to divisions within the party that have something to do with what all concerned describe as a "complicated" relationship between Ms. Byrne and Mr. Finley, and how it ended.

The official story – which is true – is that with Mr. Finley too sick to run the Conservatives' 2011 campaign, his deputy stepped in for him. But that does not seem to be the full picture.

According to Mr. Finley's friends, although he recognized that he had to take a step back, he was not eager to remove himself from the equation altogether, and was upset by the way he was treated during the transition process. They say that Ms. Byrne was part of an effort to elbow him out, in part by convincing Mr. Harper that Mr. Finley's drinking was making him increasingly erratic, and that his ethical standards were problematic, particularly after the "in-and-out" controversy in which the party had been fined for violating election-spending limits.

Lending credibility to this account, some of Ms. Byrne's friends and allies still today echo the arguments against Mr. Finley that were allegedly used against him behind the scenes.

In any case, once Mr. Finley was out of the picture, a good chunk of the campaign team that he had assembled followed. In some cases, those departures were voluntary. In others – most prominently that of Patrick Muttart, the brains behind many of the Conservatives' marketing efforts, who was turfed in the middle of the 2011 campaign over a strange little controversy involving a dubious leak to the Sun newspapers about Liberal leader Michael Ignatieff – they were not.

This was not all Ms. Byrne's handiwork. Conservative campaign chair Guy Giorno has also held sway over personnel decisions. And of course, the buck ultimately stops with Mr. Harper.

But there is a view, expressed by some Conservatives familiar with Ms. Byrne's interactions with the Prime Minister, that she can play to his worst instincts – including his willingness to unsentimentally discard people once they are no longer useful to him.

Beyond Mr. Finley and his circle, that might also have included Nigel Wright, the Bay Street heavyweight with whom Ms. Byrne had an unpleasant relationship – his wonkishness a poor fit with her hyper-partisanship.

Few seriously blame Ms. Byrne for Mr. Wright's 2013 exit as chief of staff, following the revelation that he cut a personal cheque for Mike Duffy to help the scandal-plagued senator out of his expenses mess. But after she was brought back into government from the party side to put her issues-management skills to work, some saw her fingerprints on Mr. Harper's shifting from merely distancing himself from Mr. Wright to publicly accusing him of "deception."

Then there are times, such as the shunning of Mr. Hudak, when Mr. Harper may not even know about the score-settling within his party, or else chooses to ignore it.

The net effect is that plenty of Conservatives who have previously contributed to their party are currently sitting on the sidelines, and even some still involved are taking shots.

Conservative dysfunction is nothing remotely akin to the civil war the previous Liberal government went through, because there is no Paul Martin to Mr. Harper's Jean Chrétien. Any party this far into power could have it much worse, and that might owe to Ms. Byrne's serving, as one Conservative put it, as the PM's "praetorian guard."

Nor is it terribly unusual for a campaign manager to consolidate power around her, the way Ms. Byrne seemingly has, by jettisoning people who surrounded her predecessor in favour of those she trusts – the likes of Mr. Teneycke, and others with lower profiles.

But the pressure will be on her, in the months ahead, beyond the degree to which it was previously. Fairly or not, the last campaign was perceived by many as having been planned out by Mr. Finley. There will be no question, in the minds of Ms. Byrne's admirers and detractors alike, who will be responsible for the operations of the coming one.

Sticking to the basics

In Mr. Finley's day, he and others, including Mr. Muttart, would jet around the world looking for campaign strategies they could learn from. Australia, where they had close ties with the right-leaning Liberal Party, was a particular favourite; it was from winning campaigns there that they borrowed, among other things, a highly centralized model for managing resources in target ridings.

Ms. Byrne has made little secret that she considers such trips to be frivolous junkets – "somewhat work-related self-indulgence," as one of her friends put it. Other than sometimes attending the annual Conservative Political Action Conference south of the border, her work-related travel is almost always within Canada, mostly to train and supervise candidates and organizers.

That speaks to a broader philosophical difference between the current campaign manager and her predecessor. Mr. Finley took it as his mission to modernize his party, if not personally, then by surrounding himself with whiz kids. Ms. Byrne is all about sticking to the basics.

"Many organizers are always looking at the next big thing," is how Mr. O'Toole, the veterans affairs minister, puts it. "Jenni will focus on delivering with hard work and discipline."

Over the past year, a digital team working out of the Conservatives' headquarters helped them bolster their financial advantage over the other parties by stepping up online fundraising. There was some expectation that its members would shift into the campaign office and continue working together, possibly with a broader mandate to engage or communicate with voters. Instead, Ms. Byrne opted to break them up, with a couple of the team's members let go, others reassigned, and the group's leader, Lanny Cardow, essentially left off the campaign team and staying in the party office to continue focusing squarely on raising money.

That dismantling has been taken by some Conservatives as evidence of Ms. Byrne being incurious, and her commitment to the tried and true being taken to an extreme.

By all accounts, she is deeply skeptical of social media's effectiveness. Her interest in using analytics to predict voting patterns is limited. To the extent that she has sway over advertising, which is not something in which she tends to deeply involve herself, she can be expected to push for messaging and mediums along the lines of what has worked before.

The danger in such traditionalism is that the Conservatives may fall prey to a familiar problem of long-time incumbents. Having run the most sophisticated of the major parties' recent campaigns, they could be surpassed operationally by hungry rivals who, by virtue of their losses, are more willing to experiment.

Ms. Byrne, based on conversations with those close to her, would likely counter that all the shiny objects in the world won't matter if the Conservatives' advantages are properly put to use. They have the most seats, the most money, the best voter data, the most discipline, the strongest support base and a leader who connects with it; they just need to execute.

If that's true, she may well be the perfect person for the role. The campaign manager's job is largely to make sure everyone else is doing theirs, and holding people to account is Ms. Byrne's specialty. The same goes for putting out multiple fires every day. Helping on both those fronts, and plenty of others besides, is the fact that, after all her time working in the trenches, she has an encyclopedic knowledge of the country's political map and the Conservatives' organization in every corner of it.

Ms. Byrne also has a quality both underrated and rare in political circles: decisiveness. "With some people, a decision on which shade of blue to use for campaign materials could last about a day," a Conservative who has worked with her and is not generally a fan, says admiringly. "With Jenni, it would last about a minute. She will make a decision and not second-guess it."

Beyond keeping the campaign focused and not bogged down sweating the small stuff, that could come in handy if pivots are necessary. Because the Conservatives ended up winning a majority, it's easy to forget that the last campaign did not go remotely the way they had expected, and in the final days they had to adapt their tactics to the NDP's surge. Although Ms. Byrne's responsibilities are more operational than strategic, myriad quick decisions could be needed in the event of a sudden shift this time around.

But in preparing for the campaign, the courage of Ms. Byrne's convictions means there will be no reinventing the wheel. That leaves an obvious question about what will happen when reinvention is needed in the years that follow.

What next, for the party and for Jenni Byrne?

The two-dimensional henchwoman caricature of Ms. Byrne that is common in the capital does not entirely hold up to scrutiny.

Although former PMO staffer Rebecca Thompson generally got on well with Ms. Byrne, she is not among her closest friends. After Ms. Thompson left government to work for Sun News Network, the two were only infrequently in touch. But when Ms. Thompson's mother died suddenly in 2013, she recalls, an "extremely giving" Ms. Byrne – who had lost her own mother three years earlier – reached out more than anyone else she knew in politics.

Mr. O'Toole says that, when Ms. Byrne stayed with his family while helping out with the 2012 by-election campaign that brought him to Parliament, she was so good with his kids that, by the time she left, they were calling her Aunt Jenni.

People with whom she socializes, over drinks at bars or at game nights she has been known to organize, talk about her loud, infectious laugh. A couple of them describe her as "bubbly."

But it's also true that Ms. Byrne has seemingly made a project of keeping her more endearing qualities hidden from public view – of being respected and feared rather than liked – and she has probably helped her career in the process. Since Mr. Harper's first leadership campaign, she has never been terribly concerned with ingratiating herself to anyone other than him. That is a rare characteristic in a political world filled with people plotting their next career move, and it is a trait he is known to appreciate.

That, along with the fact that she has not wearied of the backroom life the way most political staffers do, helps to explain why she has lasted longer around the Prime Minister than most people. She has been unfailingly loyal to him, has earned his trust to go about her job as she sees fit, and is not the sort likely to annoy him by writing her memoirs.

All that is also why her future when Mr. Harper makes his exit – either involuntarily after this year's election, or perhaps voluntarily before he has to lead his party into another one – is decidedly up in the air.

"I don't think she has given much thought, in any serious way, about what comes next for her," says Chris Froggatt, a former colleague and onetime chief of staff to John Baird, with whom she has remained friends. "While I'm sure it's at the back of her mind, she has always been more consumed with the task ahead."

Some of her other friends express concern that she has devoted her entire adult life to the Conservative Party, rebuffing those friends' suggestions that she move on before she has to, to make more money or have more time for her personal life. (Speculation about whether she should try to find a long-term partner or have kids is something else her single male colleagues don't have to deal with as much.)

It's possible that in the eventual leadership campaign to replace Mr. Harper, she could align herself with Jason Kenney, currently the defence minister, with whom she is said to be on good terms. But a downside of making lots of enemies is that she could have too much baggage for a prospective new leader looking to make friends.

"Once Harper falls, Jenni's going to get ripped apart by a lot of that crowd," said one well-connected Conservative, referring in particular to those who were close to Mr. Finley.

"I don't think she's kidding herself that when the Prime Minister goes, there'll be a role for her within the party," said another who has worked with her. "She's self-aware enough to know how things work."

Considering the tenacity she has shown over the past 18 years, she will presumably land on her feet one way or another. But for someone who has been so central to her party's evolution, the uncertainty about what awaits her is perhaps fitting.

The planned departure of Justice Minister Peter MacKay, Mr. Harper's old partner in merging the right, served as a reminder this week of just how long the current Conservative era has lasted. And nobody really knows what the party will look like after the only leader it has known – a leader who has, with Ms. Byrne's assistance, held unusually strong control over it – is gone.

Perhaps, the party's professionalization complete, her brand of discipline will have outlived its usefulness. The oppositional mentality, the fear of getting too close to the Ottawa establishment, may have fallen out of vogue. The connection to a place like Fenelon Falls might not be as valued. The leeway to settle scores may not be granted. If the next leader doesn't have his or her own version of Ms. Byrne, it may be because one isn't needed or wanted.

But her fingerprints will be all over the party, for better or worse, when it is handed over. "She's a pretty polarizing figure," says one of the people who worked alongside her over the years. "Either people like her or they can't stand her."

Mr. Harper could easily be described the same way. Neither he nor Ms. Byrne probably minds. Their results to this point, and in the campaign this fall, will speak for themselves.

Backstory from Adam Radwanski:

Save for Stephen Harper himself, few people have had greater influence in shaping his version of the Conservative Party of Canada than Jenni Byrne. But because she has gone out of her way to avoid the spotlight, she is less well known to Canadians than are many political operatives with considerably less power.

That made an assignment to tell Ms. Byrne's story both daunting and necessary. It is difficult to profile someone who is not willing to meet, let alone one who is rarely seen in public, and who has let it be known that she doesn't think much of other Conservatives offering their perspectives or opinions to journalists.

Fortunately, many of Ms. Byrne's colleagues and contemporaries nevertheless proved willing to speak, provided our conversations were entirely or primarily on a not-for-attribution basis. In at least a couple of cases, it was clear that they had spoken to Ms. Byrne about it in advance and had settled on a few talking points. (One prominent Conservative accidentally sent me an e-mail, intended for her, in which he asked for key messages and promised to report back.) But of the roughly 30 people who I interviewed this spring, most were candid in their assessments.

Ms. Byrne is someone who inspires strong feelings both positive and negative, and where her friends and rivals offered conflicting accounts, I've tried to reflect both perspectives. Any and all assertions about how she has approached her job came from multiple sources.

As with the Prime Minister himself, it is important to get beyond the mystique of the people around him. With this story, I've tried to provide a window not only in to Ms. Byrne, but also in to the governing party she has helped build.

Adam Radwanski is a National Newspaper Award-winning political writer for The Globe and Mail, who is currently covering the run-up to the 2015 federal election. He served as Ontario columnist for five years prior to his current assignment, and before that was a member of The Globe's editorial board.