Nikki Haley Endorsed by Gov. Chris Sununu of New Hampshire

Gov. Chris Sununu of New Hampshire endorsed Nikki Haley for the Republican presidential nomination at a campaign event Tuesday evening, casting her as a fresh face for the party who could take on the elites in Washington and move the nation past the “nonsense and drama” of former President Donald J. Trump.

“We are all in for Nikki Haley,” Mr. Sununu said to loud cheers at a ski area in Manchester, adding that her momentum was “real” and “tangible” and that her poll numbers and ground game have been “absolutely unbelievable.”

Pacing in the middle of the audience, Ms. Haley called it “a great night in New Hampshire.” “It doesn’t get any better than this — to go and get endorsed by the ‘Live Free or Die’ governor is about as rock-solid of an endorsement as we could hope for.”

The endorsement is a significant victory for Ms. Haley, who is trying to establish herself over Gov. Ron DeSantis of Florida as the main alternative to Mr. Trump and has gained ground in New Hampshire polling in the past month.

Mr. Sununu, a Trump critic who is serving his fourth and last two-year term as governor, was re-elected last year by more than 15 percentage points and is popular in the state. He was seen as a top recruit for the Senate last year but declined to run, and he also chose not to run for the Republican presidential nomination himself — saying at the time that he thought he could have more influence as an external voice than as a candidate.

On the 2024 presidential campaign trail, Mr. Sununu stumped with Ms. Haley, Mr. DeSantis and former Gov. Chris Christie, as he weighed which of the three to back. In an interview last month, he said he would talk over his decision with friends and family over the Thanksgiving break. He said he was looking for someone who could beat Mr. Trump and who could connect with voters on “a very retail level.”

Before the raucous crowd in Manchester, Mr. Sununu lauded Ms. Haley as a traditional Republican with the executive experience to secure the border, tackle mental health needs and ensure low taxes and limited government. He urged New Hampshire voters to turn the page on this era’s politics, taking shots at both President Biden and Mr. Trump. “We have a president who is more concerned about nap time,” he said. “We have a president who is worried about jail time.”

In a news conference after the event, Mr. Sununu and Ms. Haley shot down suggestions that Ms. Haley might choose Mr. Sununu as her vice president should she win the nomination. “I think he is fantastic, but he has told me he doesn’t want anything to do with V.P.,” she said.

Ms. Haley told reporters she had been more focused on winning over voters than scoring endorsements from elected officials, but she nevertheless called Mr. Sununu’s support a huge win for her bid. Mr. Sununu argued the race had now become a contest between only two people — “Nikki Haley and Donald Trump.”

“There’s differences with us,” Ms. Haley said when Mr. Sununu was asked if he believed Ms. Haley had sufficiently confronted the former president. “Anti-Trumpers don’t think I hate him enough. Pro-Trumpers don’t think I love him enough. The end of the day, I put my truths out there and let the chips fall were they may.”

Given his popularity and his proven ability to win as a Republican in a state that leans Democratic, Mr. Sununu could help sway the moderate Republicans and independents whom Ms. Haley is counting on to give her a strong showing in New Hampshire’s first-in-the-nation primary on Jan. 23.

Undeclared voters, who can participate in the Republican primary, now make up roughly 39 percent of voters in the state, a greater slice of the electorate than either Democrats or Republicans. And with no competitive Democratic presidential primary next year, they are expected to play an even larger role in the Republican contest.

“It is really a big move,” Matthew Bartlett, a former Trump appointee and Republican strategist who is unaligned in the race, said of Mr. Sununu’s backing. “It is really the last chess piece to fall in line before Election Day, and it is not to be underestimated.”

But just how much weight it will carry is an open question in a primary in which nothing — not endorsements, not debates, not 91 felony charges — has changed the basic dynamic: Mr. Trump is the overwhelming favorite, and everybody else is fighting for second place.

The Sununu endorsement was first reported by WMUR earlier on Tuesday.

Mr. DeSantis received two of the biggest endorsements available in Iowa — those of Gov. Kim Reynolds and the evangelical leader Bob Vander Plaats — but has yet to make significant gains on Mr. Trump there. Still, campaign officials for Mr. DeSantis and Mr. Christie downplayed the impact of Mr. Sununu’s backing.

“This puts us down one vote in New Hampshire and when Governor Christie is back in Londonderry tomorrow, he’ll continue to tell the unvarnished truth about Donald Trump and earn that one missing vote and thousands more,” said Karl Rickett, campaign spokesman for Mr. Christie, who has made New Hampshire his do-or-die state.

Ray Buckley, the chairman of the New Hampshire Democratic Party, criticized both Ms. Haley and Mr. Sununu in a statement. “No matter how much Nikki Haley or Chris Sununu try to spin Granite Staters, the reality is they’re both MAGA extremists who spent years cozying up to Donald Trump,” he said.

At the ski area in Manchester, a prospective voter solicited a low exclamation of “oohs” from the crowd when she asked if Ms. Haley would ever consider the vice presidency given Mr. Trump’s dominance in national and state polls.

“It is not that big of a deal,” Ms. Haley responded, calming the crowd and prompting some laughter, “because what you have to know is I don’t play for second.”

In the audience, Dan Silverman, 53, an undeclared voter who leans Republican, said he wasn’t particularly keen on any of the contenders in the Republican primary and was concerned about some of Ms. Haley’s “bombastic language” on foreign policy. But after watching her speak, Mr. Silverman, who teaches information systems courses at the University of New Hampshire, said he enjoyed her remarks. “I am coming around,” he said.

Nearby, Bruce LaRiviere, 65, a retail salesman, said he was set on voting for Ms. Haley, whom he admired for her calls for term limits and competency tests for elected officials. He hoped Mr. Sununu’s endorsement would provide her the boost she needed to beat Mr. Trump, who he said was a force of a “noise and aggression.”

“She’s very conservative,” he said. “I like the way she is going to try to change Washington.”