HAMPTON, N.H. — With Bernie Sanders and Pete Buttigieg battling to win Tuesday's primary here and seize the momentum in a highly unpredictable race, another drama is playing out with serious implications for the other high-profile candidates in the Democrats' once-sprawling field.

Sen. Elizabeth Warren is facing the prospect of losing badly in a state neighboring her home of Massachusetts, while Joe Biden’s campaign is bracing for another potentially humiliating defeat and, as a result, a new round of anxiety among its top donors and questions about the viability of a former vice president once seen as the Democrats’ best hope to defeat President Trump.

The grim question facing Warren and Biden is not whether they can win New Hampshire, according to strategists, but how low they will finish — and what that result would mean for their candidacies.

Two days before voters head to the polls, Biden advisers were already eager to move on, hoping the former vice president would do better with Nevada and South Carolina’s more diverse electorate. But there are growing concerns, even inside his campaign, that financial resources are being strained ahead of an upcoming stretch that will only get more expensive as the race shifts into a national campaign.

Biden in recent days has retooled his stump speech, focusing on the stories of those he has met on the trail, and growing emotional as he speaks about the 2015 death of his oldest son, Beau.

But at times, he struggled to connect with voters. On Sunday morning, at an oceanside ballroom here, Madison Moore took the microphone and warned the former vice president that the question she was about to ask was going to be a bit mean.

“How do you explain the performance in Iowa and why should voters believe that you can win the national election?” asked the 21-year-old student at Mercer University in Georgia.

Biden said it was legitimate question, but then turned the spotlight back on her, asking: “Iowa’s a caucus. Have you ever been to a caucus?”

When she indicated yes, he rebuked her: “No, you haven’t. You’re a lying dog-faced pony soldier.”

The phrase was an allusion to a line in a John Wayne movie that Biden had used before. Even so, Moore said she was shaken and flummoxed at his reaction. Biden went on to say that the caucus posed challenges to his campaign, and he conceded that they were less prepared.

“I congratulate Pete, I congratulate Bernie,” he said. “They were really well organized. Better than we were in Iowa.”

As the Democratic presidential candidates sprint to the finish ahead of Tuesday’s New Hampshire primary, the momentum is clearly behind Sanders and Buttigieg. Public polling suggests that Biden’s main competitors in the race for third place are Warren and Klobuchar, who finished third and fifth in Iowa, respectively.

A finish of fourth place or lower by Biden in New Hampshire would also likely give a boost to the campaign of former New York mayor Mike Bloomberg (D), who has cast himself as the chief “establishment” alternative to Sanders and who is forgoing the early states in favor of the March 3 Super Tuesday contests. Bloomberg has already invested hundreds of millions of dollars in advertising in those states.

For his part, Biden has simultaneously sought to play down expectations and ramp up his attacks on his rivals over the weekend. “Now, let’s be realistic; I think it’s always going to be an uphill fight,” he said in an interview on ABC News’s “This Week” that was taped Saturday.

Pointing to Sanders and Warren, he added: “When you’re running against two people who are neighboring senators, you know the deal. . . . So I think it is an uphill fight, but I think it’s a fight we will do well in.”

After his Iowa loss put a dent in his campaign’s main selling point — his electability — the former vice president has responded by doubling down on his argument that he is the candidate best poised to bring together the diverse parts of the Democratic coalition.

“No one has ever won the nomination without being able to get overwhelming support from the African American community,” Biden said on “This Week.” “And so far, no one’s been doing that but me.”

Biden also on Sunday took a swipe at Sanders’s health-care plan, saying it was too expensive and would take too long to enact. The Vermont senator’s biggest problem, Biden argued, was that he wasn’t being fully truthful with the American people.

“Look, the one thing I think the public is looking for as much as anything is authenticity,” Biden said. “Just tell me the truth. And if you don’t know, don’t ask me to buy a pig in a poke.”

Alan Kessler, a longtime Democratic fundraiser and donor and one of the Biden campaign’s top bundlers, said he was concerned by the distance between Biden and the top two finishers in the Iowa caucuses.

Biden’s donors and fundraisers are not expecting him to win in New Hampshire and are managing the expectations of other donors, reminding them that Iowa and New Hampshire are driven by support from mostly white voters and that Biden’s strength lies with a more diverse coalition in Nevada and South Carolina.

“The finishing fourth wasn’t, to me, as much of a situation as the disparity between him and Mayor Pete and Sanders,” Kessler said. “The good thing is, a lot of my compatriots feel the same way, which is: Wait and see. The narrative all along has been Nevada to some degree, and certainly South Carolina.”

Donors are “worried and concerned” about Biden’s campaign, he said, and are advising the candidate to take a more aggressive approach — advice many of them are giving on donor calls with Biden.

“Things have to change a little bit. He’s got to interact with the media in a less scripted way. I think that’s happening. He’s got to come out swinging — no longer Mr. Nice Guy. If that turns off some voters, so be it,” Kessler said.

As Warren and Klobuchar spent their Sunday on the trail wooing voters, they, too, tamped down expectations for New Hampshire.

Warren was largely hewing closely to the stump speech and event format that she’s used for the past 13 months. The speech uses her hardscrabble biography to explain how she became interested in the financial woes of the middle class and how she became focused on leveling the playing field for Americans.

Warren’s been so unwavering that reporters pressed her repeatedly Sunday on whether she plans on making any changes.

In response to a question from a reporter in Concord about whether the state represents her last stand, Warren replied, “It looks like it is going to be a long battle to the nomination.”

“I’m in it for the long haul,” she added. “I built a campaign to be in it for the long haul.”

Warren demurred when a reporter pointed out that a number of attendees left her Concord town hall early.

“It seemed like to me a pretty enthusiastic crowd,” she said.

Warren allies say that the field is so fractured and fluid that they believe she still has a chance to do well later in the calendar even if she only musters a third-place finish here. If Biden collapses, his support from minority communities would be up for grabs — and Warren’s boosters believe it’s unlikely that nonwhite voters will flock to Buttigieg or Klobuchar. Should Sanders prevail in New Hampshire with a big win, they hope Democrats will look for a more unifying candidate who can also fire up the liberal base of the party.

Warren’s campaign on Sunday sent an email to supporters noting that it had set a $2 million fundraising goal last week and “blew right past it.”

The email came one day after Klobuchar’s campaign sent its own missive to supporters noting that the Minnesota senator had raised more than $2 million in the wake of Friday night’s Democratic debate.

Klobuchar has been holding as many as five or six campaign events a day; on Sunday, she deployed her husband, John Bessler, on the trail in New Hampshire as well.

Recent polling shows that many New Hampshire voters, like 59-year-old Ken Meade, remain undecided.

Meade, of Laconia, had previously supported Sen. Kamala D. Harris (D-Calif.) and is now torn between Klobuchar, Warren and several others — but he noted that he believes Biden, 77, and Sanders, 78, are both too old to be president.

“When I get to the voting booth, it might just be gut,” Meade said after attending Warren’s town hall Sunday. “At that moment, who do I think has the best chance of beating Trump?”

Sonmez reported from Washington, and Viser reported from Hampton, N.H., and Dover, N.H. Annie Linskey in Concord, N.H., contributed to this report.