Still, the night appeared likely to belong to Sanders, based on the initial results. With about a quarter of precincts reporting, he had 28 percent, while Buttigieg was at 23 and Klobuchar at 20. Elizabeth Warren was at 11 percent and Joe Biden at 8 — both below the threshold required to win delegates.

Shortly after the polls closed, meanwhile, two long-shot candidates, Andrew Yang and Sen. Michael Bennet, dropped out. Yang, the quirky entrepreneur and political novice, had vastly exceeded expectations in the primary, but he was counting on a strong finish in New Hampshire that did not materialize.

Going into the night, Sanders was not only preparing for a widely expected victory in New Hampshire, but eclipsing Biden for the first time nationally in a Morning Consult poll.

Biden was just desperate to escape.

Following a dismal showing in Iowa and with low expectations here, the former vice president planned to leave New Hampshire on Tuesday night for more favorable ground in South Carolina. Rather than Biden, it was a surging Pete Buttigieg whose momentum Sanders was seeking to blunt.

“We have a chance to do really, really well here tonight,” Sanders said at a polling place in Manchester. “We have an agenda that speaks to the needs of working families all across this country who in many cases feel that Washington has turned its back on them.”

A Sanders victory would not be unexpected after his thrashing of Hillary Clinton in New Hampshire in 2016. But if he does win, it will mark his second strong showing of the campaign, after a one-two finish with Buttigieg in a chaotic Iowa contest whose outcome has yet to be called.

Biden, meanwhile, has been reeling after finishing fourth in Iowa.

In an interview that aired Tuesday on CNN’s “New Day,” he said he's "anxious to get to South Carolina and Nevada” and that Super Tuesday is critical to his prospects.

“I view this as, you know, a package of four, just out of the gate,” he said. “And I don’t know how you can judge who is going to likely be able to win the nomination until you have the African-American vote and the Latino vote. And that doesn’t come until later.”

The outcome on Tuesday was unlikely to end any top-tier candidate's campaign, regardless how bad. And rather than beginning to settle the Democratic Party's nominating contest, the result was likely to only muddle it further.

In addition to Sanders, Biden, Buttigieg and Elizabeth Warren, one candidate polling lower nationally, Amy Klobuchar, could rejuvenate her campaign in New Hampshire. A Boston Globe/WBZ-TV/Suffolk University poll on Sunday put her in third place in the state, ahead of both Biden and Warren.

“Something’s happening here,” Klobuchar said at a polling location in Manchester Tuesday morning. “And we just want to seize the moment, so I’m going to work my heart out all day.”

Nor would a second-place finish to Sanders in New Hampshire be crippling to Buttigieg. But it could make it more difficult for him to make inroads in the states that follow.

In an interview on NBC’s “Today” show that aired Tuesday, Buttigieg said that “voters of color who are laser-focused on defeating this president, more than anything else, want to know that you can actually win,” suggesting strong performances in Iowa and New Hampshire could help him as the campaign turns to Nevada and South Carolina.

Still, the former South Bend, Ind. mayor has only 4 percent support among black Democrats, according to a Quinnipiac University poll Monday.

For moderate Democrats, the most closely watched candidate Tuesday may not be a centrist at all, but the progressive alternative to Sanders, Warren. Following a third-place finish in Iowa last week — and with polls suggesting she could tumble further in New Hampshire — many moderates fear that if Warren slips out of contention, the party’s left flank may coalesce around Sanders.

Warren, of neighboring Massachusetts, could keep the race on the left competitive with a resurgence in New Hampshire. Asked if she was more pragmatic than Sanders, Warren told reporters, “I’m determined to get things done, I’ve already done things and seen the difference it can make.”

Moderate Democrats are intently interested in Warren’s viability, hopeful that she might continue to draw some progressive support away from Sanders and split the left flank’s vote. The concern is especially pressing with so many centrist candidates dividing support, including billionaire Michael Bloomberg, who is bombarding the country with his television ads.

Buttigieg told NBC News on Tuesday that it “would be very difficult” for Sanders to win the nomination.

"It's not just because of the labels. It's because of the approach," Buttigieg said.

Marc Caputo, Alex Thompson, Elena Schneider, Myah Ward and Quint Forgey contributed to this report