When the 2020 Democratic presidential candidates descended on New Hampshire last weekend, Beto O’Rourke returned to the campus where just months earlier he’d packed hundreds onto multiple floors of Keene State College’s red-bricked student center.

This time, the students and locals who came to hear the former Texas congressman Friday barely filled half the room. Yet when asked whether the deflated turnout was disappointing, O'Rourke was undeterred.

“I'm really grateful for everyone who would forego a perfectly fine meal or a dinner date to spend some time on a Friday night with a candidate for the presidency,” O'Rourke said.

Halfway across the country, Pete Buttigieg was hitting the Iowa airwaves with the first TV ads of his campaign, deploying some of the eye-popping $25 million he raised in a mere three-month span. But he, too, was fending off growing concerns that his campaign — once an unlikely juggernaut — was losing steam.

“You kind of got lost, Mayor Pete,” said radio host Charlamagne tha God as he interviewed the South Bend, Indiana, mayor on his show, “The Breakfast Club.” Putting a finer point on Buttigieg’s performance in the first debates, he added: “Do you think you sucked?”

Democratic 2020 presidential candidate and South Bend Mayor Pete Buttigieg greets supporters before the New Hampshire Democratic Party state convention in Manchester, New Hampshire on Sept. 7, 2019. Gretchen Ertl / Reuters

Two boyish Democrats from conservative states with their eyes on the Oval Office, Buttigieg and O’Rourke both once took the political scene by storm, offering a fresh face and innovative tactics in a field dominated by septuagenarians and longtime Washington denizens.

Now as they prepare to participate in Thursday night's presidential debate, both find themselves struggling to maintain relevance in a primary field led by three front-runners: Former Vice President Joe Biden and Sens. Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt.

As they seek to reinvigorate their campaigns, Buttigieg’s and O’Rourke’s contrasting approaches offer a window into the broader tension pulsing through the primary: whether to nominate a “safe choice” to defeat President Donald Trump at any cost or hold out for a more inspiring, unconventional candidate who can carry the Democratic Party into the future.

Ben LaBolt, who worked on both of former President Barack Obama’s campaigns, said both Buttigieg, 37, and O’Rourke, 46, are campaigning as outsiders and generational change agents, skewering the traditional rules of campaigning and thrusting themselves in front of audiences that other candidates are not.

“Can there only be one candidate in that lane over time?” LaBolt said. “Yes, but there can only be one nominee, too.”

For O’Rourke, the challenge is to re-insert himself into a conversation where he once dominated. After surging into double digits in multiple polls in March, he’s seen his numbers dwindle to the low single digits, notching just 3 percent in a new Washington Post-ABC News poll.

His new strategy includes abandoning the typical laser-like focus on Iowa and New Hampshire in favor of a guerilla-style campaign aimed at non-traditional voters in unlikely places. In the wake of a devastating mass shooting in his hometown of El Paso, Texas, O’Rourke has sought to reorient his campaign squarely around the issue of gun control, hoping that if he can’t stand above his competitors, at least he can stand apart.

Buttigieg’s challenge is more difficult to diagnose. Flush with campaign cash — he raised more between April and June than any other candidate — Buttigieg is attracting impressive crowds that rival those of the front-runners. But that tangible enthusiasm on the campaign trail is not showing up when pollsters ask who voters plan to pick next year.

Unlike O’Rourke, Buttigieg has doubled down on his early-state playbook: Investing as much as possible in Iowa and New Hampshire in hopes that a strong showing in the first two states will catapult him forward next year.

“As the race thins out, as our message continues to land, I think that we've got the right game plan to consolidate our position toward the top and make our way to the nomination,” Buttigieg told NBC News in a recent interview while campaigning in Tipton, Iowa. “But it's not going to happen overnight, and we can't get too caught up with changes from week to week in poll numbers.”

If Buttigieg’s path to victory relies on patience, it’s one borne out by primary voters who say the large remaining field of candidates is clouding their decision.

Kara Ewinger, an Iowa resident who worked for former President Obama’s 2008 and 2012 campaigns, said she wasn’t sure why Buttigieg’s poll numbers lag so far behind his fundraising and crowd sizes, but surmised it was because when it comes to candidates, “there’s just so many to choose from.”

“Maybe something to do with age, experience, not knowing enough about him,” Ewinger said of the millenial mayor after hearing his stump speech for the first time in Burlington, Iowa. Although undecided, she added: “All they have to do is come listen to him live and they can see that he can take on Trump.”

O’Rourke, who had burst onto the national stage in 2018 by nearly ousting GOP Sen. Ted Cruz, crested almost immediately after entering the race in March.

Just a month later, Buttigieg jumped into the race and quickly surged past of nearly 20 other competitors into third place in New Hampshire and Iowa, stealing O’Rourke’s thunder and perhaps some of his supporters as well.

But that was April. Soon a fatal shooting of a black man by a South Bend police officer and an ensuing community uproar helped crystalize Buttigieg’s challenge in appealing to black voters who play a critical role in the Democratic primary — a obstacle Buttigieg has yet to prove he can overcome.

Months later, the forces of political gravity have pulled Buttigieg into fifth place and single digits, even as he builds out a massive campaign infrastructure of more than 300 people.

Eager to dispel the notion that he’s peaked, Buttigieg’s aides have cast his current interlude away from the limelight as part of the plan all along.

His campaign has said the next phase of his effort entails ramping up a campaign capable of carrying him to victory by converting enthusiasm into actual votes. This month he opened dozens of offices in the early states, and now has more in New Hampshire than anyone else.

Although the unflappable small-town mayor and the frenetic, profanity-prone Texan are stylistic opposites, it’s not lost on some voters that Buttigieg and O’Rourke cross into similar territory when it comes to offering a break from the status quo.

“I've been really looking hard at Beto O'Rourke and Buttigieg because they are younger,” Michael Overacker, an independent, said after hearing O’Rourke speak recently in Bland, Virginia. “I really think they need some young blood in politics now.”

The stop in Bland County — in the most pro-Trump stretch of Virginia in 2016 — mirrored others O’Rouke has made in reliably conservative states in recent weeks.

He's also visited Arkansas, where he touted the need for background checks while at a gun show, and Mississippi, where immigration was his focus as he spoke at a Latino grocery store blocks from a food processing plant recently raided by U.S. Immigration and Customs Enforcement. Along the way, O'Rourke and his campaign have emphasized his unwillingness to write anyone off.

Democratic presidential candidate former Texas Rep. Beto O'Rourke greets students after speaking at a event at Tufts University in Medford, Mass. on Sept. 5, 2019. Winslow Townson / AP

"It's the old Beto, really," former Obama strategist David Axelrod noted on his podcast, 'Hacks on Tap.' "He's behaving now like he was in the senate race. He's filled with a moral outrage."

His campaign insists it’s paying off. O’Rourke press secretary Aleigha Cavalier told NBC News that his online fundraising and social media engagements are both on the rise.

The post-El Paso O'Rourke has also appeared unburdened by typical candidate rhetorical expectations. His description of the recent mass shooting in Odessa as "f----ed up," caused some pearl clutching among Washington political observers, but the campaign doubled down.

"It’s just honest, and I think it describes the situation," O'Rourke told CNN's Christiane Amanpour. "We have to shake ourselves out of this complacency. We have to shock the conscience of this country. We have to force us to act decisively."