Donald Trump won the New Hampshire primary on Tuesday, tightening his grip on the Republican presidential nomination and bolstering the likelihood of a rematch later this year against President Joe Biden. 

The result was a setback for former U.N. Ambassador Nikki Haley, who invested significant time and financial resources into winning the state but finished second. She is the last major challenger in the race after Florida Gov. Ron DeSantis ended his presidential bid over the weekend, allowing her to campaign as the sole alternative to Trump. Haley intensified her criticism of the former president, questioning his mental acuity and pitching herself as a unifying candidate who would usher in generational change. 

The appeals failed to resonate with enough voters. Trump can now boast of being the first Republican presidential candidate to win open races in Iowa and New Hampshire since both states began leading the election calendar in 1976, a striking sign of how rapidly Republicans have rallied around him to make him their nominee for the third consecutive time. 

By posting easy wins in both early states, Trump is demonstrating an ability to unite the GOP's factions firmly behind him. He's garnered support from the evangelical conservatives who are influential in Iowa and New Hampshire's more moderate voters, strength he hopes to replicate as the primary quickly expands to the rest of the U.S. 

Haley was unable to capitalize on New Hampshire's more moderate political tradition. Now, her path to becoming the GOP standard-bearer is narrowing quickly. She won't compete in a contest that awards delegates until South Carolina's Feb. 24 primary. As the state's former governor, she's hoping a strong showing there could propel her into the March 5 Super Tuesday contests. But in a deeply conservative state where Trump is exceedingly popular, those ambitions may be tough to realize and a home-state loss could prove politically devastating. 

Haley vowed Tuesday night to stay in the race and push ahead to South Carolina. 

"New Hampshire is first in the nation; it is not the last in the nation," she said. "This race is far from over. There are dozens of states left to go." 

Republican presidential candidate former UN Ambassador Nikki Haley walks on stage to speak at a New Hampshire primary night rally, in Concord, N.H. Photo / AP

About half of GOP primary voters in New Hampshire said they are very or somewhat concerned that Trump is too extreme to win the general election, according to AP VoteCast, a survey of the state's electorate. Only about one-third say the same about Haley. 

President Joe Biden, meanwhile, won New Hampshire's Democratic primary via a write-in effort after the state party moved forward with its own contest. Biden did not appear on the ballot but allies helped him beat a series of little-known challengers. 

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Trump's position in the contest is remarkable considering he faces 91 criminal charges related to everything from seeking to overturn the 2020 presidential election to mishandling classified documents and arranging payoffs to a porn actress. He left the White House in 2021 in the grim aftermath of an insurrection at the U.S. Capitol led by his supporters who sought to stop the certification of Biden's win. And Trump was the first president to be impeached twice. 

But Trump has turned those vulnerabilities into an advantage among GOP voters. He has argued that the criminal prosecutions reflect a politicized Justice Department, though there's no evidence that officials there were pressured by Biden or anyone else in the White House to file charges. Trump has nonetheless repeatedly told his supporters that he's being prosecuted on their behalf, an argument that appears to have further strengthened his bond with the GOP base. 

As Trump begins to pivot his attention to Biden and a general election campaign, the question is whether the former president's framing of the legal cases will persuade voters beyond the GOP base. Trump lost the popular vote in the 2016 and 2020 elections and has faced particular struggles in suburban communities from Georgia to Pennsylvania to Arizona that could prove decisive in the fall campaign. 

Beyond the political vulnerabilities associated with the criminal cases, Trump faces a logistical challenge in balancing trials and campaigning. He has frequently appeared voluntarily at a New York courtroom where a jury is considering whether he should pay additional damages to a columnist who last year won a $5 million jury award against Trump for sex abuse and defamation. He has turned these appearances into campaign events, holding televised news conferences that give him an opportunity to spread his message to a large audience. 

He has no choice but to appear in court when the criminal cases begin, which could happen later this spring. 

Biden faces his own challenges, though of a different magnitude. There are widespread concerns about his age at 81 years old. Dissent is also building within his party over Biden's alliance with Israel in its war against Hamas, putting the president's standing at risk in swing states like Michigan. 

Biden championed new Democratic National Committee rules that have its 2024 primary beginning on Feb. 3 in South Carolina, rather than in Iowa or New Hampshire. That left him in something of an awkward position at the outset of the nomination process. 

But Democrats in New Hampshire defied the revamped order and held their primary on Tuesday, same as the Republicans. Biden didn't campaign, giving the state's Democrats the chance to support primary challengers including Minnesota Rep. Dean Phillips and self-help author Marianne Williamson — though many of New Hampshire's top Democrats backed a write-in campaign that Biden could still win. 

Trump traveled frequently to New Hampshire in the months leading up to the primary but didn't spend as much time in the state as many of his rivals. That included former New Jersey Gov. Chris Christie, a fierce Trump critic who enjoyed some popularity in the state but suspended his campaign mere days before Iowa's caucuses in an attempt to blunt the former president's momentum. 

Rather than the traditional approach of greeting voters personally or in small groups, Trump has staged large rallies. He has spent much of his time complaining about the past — including the lie that the 2020 election was stolen due to widespread voter fraud. 

If he returns to the White House, the former president has promised to enact a hardline immigration agenda that includes stopping migrants from crossing the U.S.-Mexico border and reimposing his first-term travel ban that originally targeted seven Muslim-majority countries. He's also said the rising number of immigrants entering the United States are "poisoning the blood of our country," echoing Adolf Hitler's language. 

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-HOLLY RAMER, JILL COLVIN, and WILL WEISSERT, Associated Press 

Colvin reported from Londonderry, New Hampshire. Weissert reported from Washington. The AP's Bill Barrow in Atlanta, Joseph Frederick in Franklin, New Hampshire, and Mike Pesoli in Laconia, New Hampshire, contributed to this report.