When the Democratic presidential primary debates get under way late next month, Pete Buttigieg, the mayor of the fourth-largest city in Indiana, and Andrew Yang, a businessman running on universal basic income who recently captured national attention for his anti-circumcision stance, will be on the stage.

Two sitting senators, current and former governors, members of the House of Representatives past and present, and a relatively high-profile former Cabinet secretary might not be up there with them.

“Not every candidate is guaranteed a spot on the Democratic debate stage, and the first debates are just over 50 days away,” Sen. Kirsten Gillibrand’s campaign said in a fundraising email Sunday morning. “The [Democratic National Committee (DNC)] could cut candidates from the stage if they don’t have 65,000 individual donors. We haven’t hit that goal yet, and time’s running out.”

While most campaign fundraising asks are hyperbolic, Gillibrand, the junior senator from New York, is in real danger of missing the first debate. Candidates can qualify one of two ways, as outlined by the DNC itself: Either register at or above 1% in at least three qualifying national polls, or secure 65,000 individual donors. And while Gillibrand has hit the polling threshold, the DNC has also capped the debates at 20 participants, and will reportedly winnow the field based on who has met the donor mark.

With 21 major candidates now officially declared in the Democratic primary, there’s a real chance an otherwise established politician could be absent from the debates, while outsider, long shot candidates will be present, a significant sign of where the energy in the race is centered in the party and a twist that could shape the primaries for months to come.

“There are so many candidates, and so many candidates that have pretty decent elected resumes,” political analyst Kyle Kondik said Monday. “There may just be not enough oxygen for all these candidates, so you’re seeing people who, in a smaller field, maybe would get more attention having a hard time breaking through.”

In a fundraising email last week, Sen. Cory Booker’s campaign also said it was 1,971 donors shy of the 65,000 donor threshold — though the New Jersey Democrat crossed that milestone soon after, according to subsequent reports. Julián Castro, the former Housing and Urban Development secretary during the Obama administration, also hit the donor mark in recent days, while Washington Gov. Jay Inslee and former Rep. John Delaney (D-MD) have yet to secure 65,000 donors.

It goes to show, Kondik said, that voters — especially highly motivated ones who ultimately choose to donate — are not necessarily looking only for a résumé, and are driven by personalities and media attention.

“We talk about these small-dollar funders as if they’re an inexhaustible supply of money for every candidate,” he added. “But only certain candidates are going to have widespread appeal among the small dollar donors. It can in some ways be a proxy for the health of the campaign.”

While a long-shot campaign has the potential to catch fire with a good debate performance, missing the debate stage entirely could spell the end of any campaign, Kondik said. And earning invitations to subsequent debates likely will not get any easier, either.

Some candidates and their advisers are concerned that even if they hit the 65,000 donor mark to secure their spot in the first debate, the DNC could raise the threshold for later debates. One anonymous aide told Politico Monday that they suspect criteria might be ratcheted up to 90,000 or 120,000 individual donors for later debates if the field doesn’t thin on its own.

“That’s why it’s so important to hit 65,000, even for those of us who have hit the polling threshold,” the aide said.

Another anonymous aide complained to Politico that the threshold basically requires chasing viral success early on in the campaign, rather than incentivizing building a winning infrastructure.

Laura Olin, a digital strategist for Obama’s 2012 campaign, said for candidates like Buttigieg or Yang, that might be true, but for politicians like Gillibrand or Booker, who have recently won Senate re-elections, virality isn’t necessary.

“So many of these other people have the infrastructure for digital fundraising in place,” she said.

Some candidates, like Yang, are drawing from completely different constituencies — people who may never have donated to a political candidate or the Democratic party before, for instance — which gives them a leg up, while Booker, Gillibrand, and others are fighting over many of the same people who make up the traditional base of the party.

Notably, the candidates struggling to hit the 65,000 threshold are also those who have relied most heavily on big money so far in the race. According a Wall Street Journal analysis, Booker, Gillibrand, and former Colorado Gov. John Hickenlooper — who also has yet to reach the 65,000 donor threshold — are the only three candidates in the race who raised the majority of their first quarter funds from contributions of $2,000 or more.

Olin said she doesn’t think it’s a coincidence that that trio has struggled to tap into a small dollar base.

“I think actually Elizabeth Warren was pretty brilliant when she made a policy plank out of not spending time on big donors. It makes a more compelling ask when she goes out to her lists,” Olin said, adding that the opposite is true for candidates who are known to be tapping into big money. “I think it is a reflection of the overall energy of where the base is.”