After the Iowa caucuses failed to produce a clear winner last week, the results of the New Hampshire primary on Tuesday night helped crystalize the presidential primary - only insomuch as it appears to be a fiercely contested battle between Bernie Sanders and any candidate who can stop him.

From a sports arena in Manchester on Tuesday night, the Vermont senator and self-declared democratic socialist claimed “a great victory” and declared the “beginning of the end of Donald Trump”, while his rivals sought to convince Democrats nervous about a Sanders nomination that they were the most viable alternative.

Sanders was trailed closely by a pair of midwestern moderates: Pete Buttigieg, the 38-year-old former mayor of South Bend, Indiana, who rose from political obscurity to effectively tie Sanders in the Iowa caucuses last week, and Senator Amy Klobuchar, who finished a promising and surprise third after presenting herself as an antidote to the “extremes in our politics”.

In a dismal finish, Senator Elizabeth Warren, from neighboring Massachusetts, and the former vice-president Joe Biden, who has led the field nationally since entering the race early last year, did not meet the threshold to earn delegates in the state.

But the primary race remains deeply unsettled, with everything to play for. All five leading candidates in New Hampshire determined to move ahead to the next series of contests in Nevada, South Carolina and beyond to Super Tuesday on 3 March, where a self-funding billionaire candidate – the former New York mayor Michael Bloomberg – lies in wait, having made the risky decision to skip the traditionally crucial early voting states.

Amy Klobuchar speaks to supporters on Tuesday night. Photograph: Gretchen Ertl/Reuters

Many in the party are worried that the fractured state of the opposition to Sanders will allow the senator to slip by, charting a similar path to the nomination as Trump did in 2016.

But the road for Sanders is hardly straightforward. In 2016, he carried the state by 22 points over Hillary Clinton. In 2020, he won by less than 2 points, raising questions about his ability to expand beyond his core base of support from young voters and liberals.

“We have been told by some that you must either be for revolution, or you are for the status quo,” Buttigieg told his raucous supporters on Tuesday night in Nashua. “Most Americans don’t see where they fit in that polarizing vision.”

At Klobuchar’s rally in Concord she said Trump’s “worst nightmare” would be to give the “people in the middle” someone to rally behind in November.

But there are immediate questions about where these two go next. With a higher national profile and and a more robust fundraising operation, Buttigieg is perhaps better poised to capitalize on the momentum from these early contests. But he has failed to prove he can win support from black and Latino voters, which will be critical.

Klobuchar, who only recently jumped into the top three after a well-reviewed debate performance on Friday and an influx of campaign donations, has even less of a footprint in the forthcoming contests. She’s scrambling to send staff to Nevada, which holds a caucus in just 10 days, on 22 February.

Warren, who has billed herself as the “unity candidate”, and Biden, who has staked his campaign on the promise that he is the most electable general election nominee, now face serious questions about how much longer they can continue.

In an election day memo to supporters, Warren’s campaign manager, Roger Lau, sought to reassure supporters that the senator was prepared to go the distance.

“The road to the Democratic nomination is not paved with statewide winner-take-all victories,” he wrote. “Warren has proven the doubters wrong before.”

Biden’s campaign argues that a reversal of fortunes awaits in the diverse states to come. But national polling has already recorded a significant drop in his support.

Sanders edged past him for the first time in a Monmouth poll this week as a pair of billionaires, Bloomberg and fellow candidate Tom Steyer, peel away critical support from black voters.

On Tuesday, Biden canceled plans to spend primary night in Nashua and instead flew to South Carolina, which has become a must-win after back-to-back losses.

Supporters of Pete Buttigieg cheer during his speech at his primary night rally at Nashua Community College on 11 February 2020. Photograph: Joseph Prezioso/AFP via Getty Images

“It ain’t over, man,” Biden told supporters at an event in Columbia, South Carolina, on Tuesday night. “We’re just getting started.”

The chaotic spectacle in Iowa, and the specter of a lengthy primary filled with jostling candidates, has left Americans with a dim view of the Democrats’ chances in November. Two-thirds of voters believe Trump will be re-elected, even though most Americans disagree that he deserves a second term, according to a Monmouth poll released on Tuesday.

Trump, emboldened by his acquittal in the Senate impeachment trial last week, has delighted in the early chaos consuming the effort to choose his opponent. At a rally on the eve of the New Hampshire primary, he asked why voters would trust the Democrats when they “can’t even run a caucus in Iowa”.

Ever the pundit, Trump offered his snap analysis on the evening’s developments on Tuesday, claiming on Twitter that Warren is “sending signals that she wants out”.

“Calling for unity is her way of getting there, going home, and having a “nice cold beer” with her husband!,” he said.

After the race was called for Sanders, he tweeted: “Bootedgeedge (Buttigieg) is doing pretty well tonight. Giving Crazy Bernie a run for his money. Very interesting!”