WARNER, N.H. — As Bernie Sanders plodded up a steep hill in the backyard of a Main Street bookstore in this tiny New Hampshire town, he was in no mood for selfies.

"Not right this second," he told the first iPhone-wielding petitioner.

"Not now," he barked, rebuffing another. "We've got a lot to get to."

But before the Vermont senator and 2020 presidential candidate could get to his revolution-inspired repertoire, he had to move the people still standing in line on the street into the green space on this picturesque blue-sky late spring afternoon.

On a day when he'd make three stops in a span of six hours, Sanders appeared annoyed this had not yet occurred.

"I'll go out and shake some hands," he instructed a pair of aides. "But," he said, lowering his voice at the sight of cameras surrounding him, "get people inside."

Dressed in a checkered Crayola blue dress shirt and navy baseball cap, Sanders then took to the street, where he exchanged swift, dispassionate pleasantries with those waiting to see him.

"Thank you very much for coming." Handshake.

"Hello." Handshake.

"Hi." Handshake.

"Hey, thanks a lot for coming." Handshake.

The exercise seemed more designed to hurry attendees along than to make connections. The ritualized procession occurred until Sanders reached a gap in the line, which in his eyes only delayed his event further.

"All right, we're trying to speed up the line!" he chided the dawdlers.

Selfies would come later, he kept telling folks. First, there was the business of his political revolution to attend to.

Supporters of Bernie Sanders protest in the media tent at the Democratic National Convention in Philadelphia on July 26, 2016. (Brett Ziegler for USN&WR)

Sanders is not a personally charismatic politician. He doesn't even try to be. When he responds to even the most adoring supporters, he rarely strives to show warmth or empathy. While there have been fits and starts at talking more about his personal biography and unfurling jokes, they largely haven't taken hold. His demeanor is Brooklyn-gruff, usually matter-of-fact and often prickly.

"Warm him up? What does that mean?" responds Sanders' longtime strategist Jeff Weaver, when asked whether he's ever attempted to coach his candidate into a sunnier disposition.

When Sanders is confronted with challenging questions by voters or reporters alike, his reflex is often to become defensive and petulant. Or as Bernie might say, he takes "umbrage." One of his favorite targets remains "the corporate media." Ask him a purely political question and you're likely to receive a diatribe about how that focus is part of the country's systemic problems, which probably explains why he's been less accessible to reporters on the trail than some of his rivals.

"If you want any person running for president to answer every question exactly the most optimal way, you're dealing with a super-scripted human being," Weaver contends. "Bernie Sanders is not super-scripted. That's not the way he operates."

Sanders devotes little attention to aesthetics and naturally scowls more than he smiles, which is rare for any successful politician, with the exception of President Donald Trump. At 77, Sanders is not one to linger or savor the moment. He wants to move things along and get to the point. During his last campaign, when he would grow irritated at the pace of his crowd's entry into a rally space, he would commonly instruct aides and eventually Secret Service agents to "Bring out more magnetometers!"

It's no surprise he was parodied as the "Get off my lawn!" candidate during his last White House bid. If a female candidate carried herself like this, she'd go nowhere.

But to his legion of loyal fans, who sprung up to support him four years ago and are eagerly on board for his second campaign, the no frills, no-nonsense mien is exactly what makes him authentic and trustworthy. Sure, former presidents Barack Obama and Bill Clinton were masterfully magnetic politicians who gave people goosebumps with their soaring rhetoric and personal rope-line encounters. But in the eyes of the most devoted Sanders supporters, they failed to achieve the scale of revolutionary change that Sanders is promising. In part, it was acting, something Bernie does not do.

"Bernie's the real deal, man. I mean, this guy is not full of it," says Vennett Weiss, a Newburgh, New York, resident who travels the country to volunteer for and see Sanders in person. "That should be his campaign slogan: Bernie Sanders: Not Full of It."

At this point in 2015, Sanders was trailing Hillary Clinton in the New Hampshire primary by 10 to 12 points. The latest survey of New Hampshire shows him in even worse shape than that this time, behind former Vice President Joe Biden by 18 points in a state he almost has to win.

There are other signs of a Sanders slide: The latest Monmouth University national poll of the Democratic race measured Sanders down 10 points in the horse race since March, the most precipitous drop of any candidate. Quinnipiac University found his unfavorable rating growing to 48 percent among all voters last month.

He's averaging about 17 percent of the Democratic vote nationally – good enough for solid second place – but still only marginally better than where he was against Clinton at this similar moment last time.

Sanders' relative stasis raises the immediate question of how he can expand his support beyond the diehards inside a party that is already almost as familiar with him as they are with the universally known Biden.

And there's also the longer term question about what his coalition of Berniecrats will do if he's not the nominee, a concern that high-level Democratic operatives are already contemplating as they attempt to game out a variety of likely primary result scenarios.

David Brock, the Clinton loyalist and co-founder of American Bridge who is neutral in this primary, worries that Sanders' polling deficit will prompt him to become more aggressive over time, working to paint Biden – or whoever the front-runner is – as a creature of the political establishment, much like he did with Clinton.

"He's fading a bit with the young people, which is not great for him," Brock says. "But I think the reaction will be, if he's stuck in the polls and not moving ... the reaction will be, 'You have to draw more contrasts with your opponents.' That's the thing that I worry about."

Sanders' third trip to New Hampshire was purposefully constructed to display him in smaller, more intimate settings than his traditional rallies allow. Each of three stops were set in outdoor yards, where hundreds could grab a scoop of ice cream from the Ben & Jerry co-founders themselves – Cherry Garcia looked to be the most popular flavor – before sitting on a lawn or under a tree to hear Sanders run through the bundle of issues he's been talking about ad nauseum for years without notes.

There is very little difference between Sanders' 2016 core message and what he's offering in 2020. He's promising Medicare for All, tuition-free college, a $15 minimum wage, overturning the Citizens United Supreme Court decision that unleashed unaccountable money in campaigns and replacing it with public financing of elections, dramatic cuts to fossil fuels, the decriminalization of marijuana and a concerted global effort to reduce the production of militarized weapons.

He's repeated it so often in so many places that even a keen observer can become numb to how radical an agenda this avowed democratic socialist is offering.

"We're not just taking on the Democratic establishment. … We're not just taking on Trump. We're not just taking on the Republican establishment. We're taking them all on," the independent senator told a crowd in Rollinsford, New Hampshire.

Lana Kangas is a 75-year-old Sanders supporter in Concord who had volunteered for Obama but eventually grew disillusioned with the 44th president.

"I feel like he was more for the establishment and corporate interests in the end," she says. "He said all the right things during his campaign, but when he finally got to be president … he didn't fight for the things. I believe Bernie will."

On Sanders, she says, "There's a trust from his past and his actions and his votes. … I just feel that Bernie is an honest person."

But while Sanders' substantive strength is credit for carrying the same message for years, the composition of the primary he's navigating now is dramatically more complex than the 2016 race that vaulted him out of obscurity. He no longer benefits from being the lone credible alternative to the front-runner. Having run before, his insurgency is less initially potent because he's taking no one by surprise. And many of his core causes have been readily adopted by his younger, more diverse opponents, prompting a considerable portion of his 2016 coalition to shop around.

"I don't feel that same sense of, 'Sanders is the only person that can deliver a progressive message,'" says Minyon Moore, a top adviser to Clinton's 2016 campaign.

Rachel Cisto, a former legislative candidate from Weare, New Hampshire, who supported Sanders in 2016, is now considering three candidates to cast her ballot for.

"It's rotating really, really rapidly between Bernie, Elizabeth Warren and Cory Booker," she says, referencing two of his Senate colleagues. "And it just depends on the day, which of them I like more."

She knows a strong core of Sanders supporters who will back him no matter what but otherwise sees many Democrats taking their time to fully commit.

Weaver believes that, in a double-digit field of candidates, carving out 35 percent of the vote is probably enough to win the first five states, which he pinpoints as Iowa, New Hampshire, Nevada, South Carolina and notably, delegate-queen California, where the Sanders campaign announced eight staff hires just last week.

"Going from 18 to 20 to get to 35 percent – that's much easier than last time in Iowa when we had to get to 50 percent and we started at 3 percent," Weaver says.

Organizationally, Sanders' campaign is months ahead of where they were in the 2016 cycle, which is tantamount to light years in a presidential campaign. At the end of July 2015, the Sanders campaign had just 28 total paid staffers, and just a few of them deployed in Iowa and New Hampshire.

Bernie Sanders meets with supporters during a rally on March 16, 2019 in Henderson, Nevada. (John Locher/AP)

In the first week of June, the Sanders 2020 operation has north of 150 total paid staffers.

Perhaps more crucially, Sanders is already boasting a volunteer army of 1 million people, including 25,000 in first-in-the-nation Iowa. The campaign counts 390,000 people in California who have either signed up on the website, hosted or attended an event or donated money to Sanders.

These volunteers will be imperative to the campaign's strategy of luring in new voters to the political process, one of the reasons the Sanders' campaign disputes the size of their deficits to Biden currently seen in public polling.

Another Sanders adviser, who declined to be named, predicts Biden's proclivity to put his foot in his mouth would also depress his lead over time, proclaiming, "I guarantee he'll lose it." To Team Sanders, the wobbly week Biden just underwent – marred by charges of plagiarism in his climate plan and a controversial stance against the public funding of abortions – is just the tip of the iceberg.

But even Sanders' admirers say the task of doubling Bernie's support will require a broadening of his coalition beyond the throngs of young and overwhelmingly white progressives who are already showing up and cheering him on at rallies.

In 2015, college senior Nate Rifkin was the first organizer the Sanders campaign hired in Iowa, after he jump-started a "College Students for Bernie" group that grew to hundreds of chapters across the country. In Iowa City, he trained his national network of campus leaders to text low-dollar donors and invite them to phone banks in Iowa. Over time, the number of volunteers and their efforts multiplied. It was the type of low-level, under-the-radar, relentless work that helped Sanders ultimately catch Clinton in the Hawkeye State.

Rifkin is not part of the campaign this time around and has not committed to a candidate but says Sanders' biggest advantage in his second run is activating his volunteer bank much earlier to touch those who may have voted for Sanders last time – more out of protest against the establishment than deep devotion to him.

"It's clearly the case that Bernie will do tremendously well among the progressive left. The question for Bernie is, that does not appear to be enough on its own to win a Democratic primary," Rifkin says. "He has to build beyond the base and reach out to voters who are not self-identified progressives. That's the challenge for him."

If Sanders is able to grow his coalition significantly, he could very well end up in the White House, given general election polling that shows him tracking ahead of Trump in battlegrounds like North Carolina and Pennsylvania. A Detroit News poll of Michigan released Wednesday placed Sanders ahead of Trump by 12 points, tying Biden's margin.

The alternative is Sanders fizzling out of the Democratic contest in a defeat that could be even harsher than what he experienced in his loss to Clinton. Sanders' brain trust believes the primary will ultimately come down to a more centrist candidate – whether that be Biden; Sen. Kamala Harris of California; South Bend, Indiana, Mayor Pete Buttigieg or someone else – and a progressive, who they see as being either Sanders or Sen. Elizabeth Warren of Massachusetts.

A narrative has begun to take hold that Warren is steadily encroaching on Sanders' turf, as evidenced by her uptick in polls and larger and more enthusiastic crowds. A third possibility for Sanders is that Warren gradually co-opts part of his coalition to assert herself as the more attractive progressive alternative to Biden – liberal enough, but not socialist.

Weaver is dismissive of the footsteps. "She's basically flat," he says. "I know all of you think she's surging. This campaign has great respect for Elizabeth Warren. That's not a dis on Elizabeth Warren, by the way. That's just where the numbers are. High single digits, 8, 9 percent."

A second Sanders adviser, under the cover of anonymity, is more cutthroat, arguing that all the wonky white papers in the world can't extract Warren from a truth: "Warren fundamentally fails a basic threshold question: Can she beat Trump? Look at all the general election polling. She does the worst of all the candidates tested. That's the DNA test debacle. It just fundamentally killed her. People want somebody who can beat Trump. She loses that argument."

"Bernie will do tremendously well among the progressive left. ... that does not appear to be enough on its own to win a Democratic primary."

While polling has shown Warren performing worse against Trump than Sanders, more recent data has shown her climbing into closer contention against the president.

At the same time, Sanders has begun regularly inserting his electability argument into his standard pitch, describing himself as "the strongest campaign to defeat the worst president in this country's history," a case he didn't attempt to make until much later in 2016.

But out in his crowds, doubts swirl among his supporters. Conversations with attendees of Sanders rallies revealed close to conspiratorial notions about the Democratic National Committee purposely sabotaging their candidate's chances – stark evidence of a broken trust that still hasn't been repaired.

"If he doesn't get cheated by the DNC, we're good. What they're doing now, putting Biden forward and stuff like that, is definitely purposeful," says Ernest Montenegro, an arts professor from Concord. "I think they did it once, they're going to do it again. If Hillary hadn't been pushy and pushed him out of the way and did everything they could to keep him with a lower profile than he really had at the time, he probably would've won."

Bob Irving, a self-employed builder at the Warner event accused the DNC of vote-stealing in Brooklyn during the 2016 primary in New York. At the time, the Sanders campaign had complained of thousands of voters being "purged" from the rolls.

"I am not convinced they won't try it again," Irving says, even though the DNC had nothing to do with New York's election system. "They are trying to get a lot of other candidates in there to weaken his chances. … They want Joe Biden because Joe will do whatever they tell him to."

Supporters of Bernie Sanders cheer during a campaign event on March 16, 2019 in Henderson, Nevada. (John Locher/AP)

Count Kangas as another who believes the DNC prevented Sanders from winning the primary in 2016 and could do it again.

"The Democrats, the establishment," she says, "that's a fear of mine."

The theory gains steam online when the progressive Young Turks network racks up tens of thousands of views on a video titled "Establishment Sabotaging Bernie Sanders AGAIN." Sanders himself told host Cenk Uygur that he fears a Biden nomination would dampen energy and excitement but stopped short of saying he'd lose to Trump.

Yet to the most rabid Sanders supporters, Bernie can't lose. He can only be cheated, foiled by dark forces.

It's this undercurrent that makes operatives like Brock ill at ease. If Sanders finishes a close second place again but is denied the nomination in favor of an establishment-emblazoned candidate like Biden, the party could again be embroiled in a bitter fight that could work to Trump's advantage.

"It has the potential to impact voter turnout on the Democratic side if people are clinging to conspiracy theories, that somehow Bernie's being thwarted by the party, which is obviously not the case," Brock says. "They become alienated from the party and system and then they sit out the election."

A revolution quashed risks a revolt.

That is the nightmare scenario, of course, something that seems possible because of everything seemingly implausible that actually transpired in 2016. For Democrats of all stripes, if the worse can happen, it probably will.

But if there is hope for the party, even after a harsh primary where Sanders is again the loser, it may lay with Weiss, the Sanders super-volunteer who treks around the country.

He despises the DNC – "Worse than ever," he says, even after this reporter lists the changes the national committee has made to holding more and earlier debates and reducing the role of superdelegates. They're still "full of it" to him.

At first he says there are a few candidates he would "never vote for at gunpoint. Biden is one of them."

But when presented with the scenario of Trump's re-election or Biden, he grimaces as his eyes roll and his head twists uncomfortably.

"If I lived in a swing state, I might get piss-drunk and go in there. I'd take all types of painkillers first and make sure I have a resuscitating machine with me. And then I'd flip the switch for that scumbag," he says.

No one said party unity was painless.