There are two types of candidates vying for the Conservative leadership — those who have a plausible chance of winning and those who don't. Only the second category is getting larger.

Maybe the people in this second group think they can pull off an unlikely upset. But if they think they can succeed by failing — that long-shot leadership bids can be parlayed into future political success — they might want to think again. The 2017 leadership race showed that losing is no way to burnish your résumé.

Four candidates have been vetted and approved by the party and are officially in the running for the top job.

Ontario MP Marilyn Gladu and Leslyn Lewis (the latter ran unsuccessfully for the party in the 2015 federal election), have each submitted the signatures of 1,000 party members (spread out across at least 30 ridings and seven provinces and territories) and the initial $25,000 entry fee. According to the party's rules, this classifies them as "authorized applicants."

As they have submitted an additional 1,000 signatures and $125,000, former cabinet minister Peter MacKay and Ontario MP Erin O'Toole have met the next threshold and are considered "authorized contestants." They will have to submit another $150,000 and 1,000 signatures by Mar. 25 to be "verified candidates" and see their names on the ballot.

But the list of hopefuls doesn't end there.

Ontario MP Derek Sloan has declared his intention to run. Rick Peterson, who finished 12th in a field of 14 in the 2017 leadership contest, is trying to mount another attempt. Former Conservative staffer Richard Décarie is hoping to run on a social-conservative platform. Another former staffer and unsuccessful Conservative candidate, Rudy Husny, posted a campaign launch video this past week.

This is not an exhaustive list of those who have expressed an interest. It will be finalized next week — Feb. 27 is the deadline to qualify as an approved applicant.

Despite the party's moves to limit the field, the Conservatives could still find themselves with another crowded field of contestants whose chances of winning are slim to none. And those contestants might not have much to show for it after it's all over.

MacKay, O'Toole and everyone else

It does seem clear that some tiers of candidates are developing.

As the front runner, MacKay occupies the first tier. He reached the second threshold for fundraising and signatures sooner than anyone else and, as of Thursday afternoon, has the endorsements of 23 Conservative MPs — including five who endorsed O'Toole in 2017. MacKay also polls ahead of the rest of the field among Conservative voters by a very wide margin.

O'Toole is in the second tier — that of the challenger. He did not hit the approved contestant threshold as quickly as MacKay did and has endorsements from only five MPs. He's also trying to occupy a lane in the Conservative leadership that isn't a perfect fit for him — running to the ideological right of MacKay.

Five Conservative Party leadership hopefuls spoke at the Progressive Conservative Party of Nova Scotia's annual general meeting earlier this month. From right to left: Erin O'Toole, Peter MacKay, Rudy Husny, Rick Peterson and Marilyn Gladu. (Stéphanie Blanchet / Radio-Canada)

Gladu and Lewis are in the third tier; they're officially in the running but have yet to show that they're serious contenders.

The rules of this leadership contest are not friendly to lower-profile candidates. The race is a short one, leaving little time for candidates to sign up new members. The bar for eligibility is high — higher than for any party leadership race in Canadian history. And by giving every riding equal weight, the leadership rules put a premium on having a national organization.

Lewis has very little in the way of a political profile, especially on the national stage — but she could end up the standard bearer for social conservatives in this race. While that could get her a significant number of votes, it almost certainly wouldn't be enough to win the leadership. The leading social conservative received just 14 per cent of votes before being eliminated in the 2017 race.

Gladu, an MP starting her second term on the opposition benches, has no endorsements and only met the approved applicant threshold this week.

The final tier includes those who aren't officially in the running yet. If they gather the needed signatures and pony up the $25,000 (which has to come from their own personal resources), they'll join the third tier and an uncertain future.

2017's ill-fated voyage

The fate of the 2017 contestants is illustrative — and, for most of the also-rans, slightly bleak. Andrew Scheer won and became the leader of the Official Opposition, with all the perks that go with the title. He lost the federal election and his political career might be over once his replacement is named.

Still, he won himself a shot at becoming prime minister — which is something. Maxime Bernier lost on the final ballot by a narrow margin. He eventually quit the Conservative Party and formed the People's Party of Canada. The PPC failed to elect a single candidate in the 2019 federal election — and Bernier himself lost his bid for re-election.

O'Toole finished third in the 2017 contest with about 21 per cent of the vote. He faces a struggle now to avoid losing a second time.

Brad Trost was a sitting MP when he lost in 2017 — but he was still challenged for the Conservative nomination in his riding and was defeated. Kellie Leitch opted not to fight for the nomination in her riding when she learned she was going to be challenged.

Kellie Leitch ponders a response as she participates in a Conservative Party leadership debate with Chris Alexander, Andrew Saxton and Erin O'Toole in 2017. (Justin Tang/Canadian Press)

Ontario MP Michael Chong has seen his signature policy — a carbon pricing scheme — roundly rejected by the party's membership. The Conservatives continue to reject any notion of supporting a carbon tax.

Pierre Lemieux and Andrew Saxton were both former MPs defeated in 2015. They both attempted a comeback in 2019 and were defeated again.

Lisa Raitt failed to win re-election in her Ontario riding of Milton. Quebec MP Steven Blaney was re-elected, but arguably has no higher a profile than he did three years ago.

Former cabinet minister Chris Alexander did not attempt a comeback and is out of politics entirely. Kevin O'Leary withdrew from the 2017 race too late to get his name removed from the ballot; he's still paying off his campaign debts.

Peterson tried and failed to secure the Conservative nomination in an Alberta riding.

There's no evidence that the leadership candidates who ended up running in the 2019 election benefited in any way from their leadership runs. With the exception of Scheer, no leadership candidate took a greater share of the vote in their home ridings in 2019 than they did in 2015.

Only one person will replace Scheer when the results of the leadership race are announced on June 27. Based on what happened last time, everyone else might want to have a solid back-up plan.