As he introduced Nikki Haley at a bar in Milford, N.H., Gov. Chris Sununu of New Hampshire was in a comfortable place — surrounded by a swarm of media cameras and local voters.
“Oh my goodness, this thing is hot,” he said into the microphone as his voice cracked in the speakers. He gave a whirlwind recap of his day crisscrossing the state with Ms. Haley and urged supporters to vote before passing the mic. “I’m going to turn it over to the star,” he said. “I’m just the lowly governor today. I’m the sherpa, as I like to say.”
Most endorsements of presidential candidates follow a standard path: a leaked announcement, a big speech in the spotlight and occasional introductions at events. Mr. Sununu’s endorsement of Ms. Haley has not been like most endorsements.
Part hype man, part campaign aide, part spokesman, part surrogate, part “new best friend” (his words), Mr. Sununu has been omnipresent on Ms. Haley’s campaign.
They have frequently held joint interviews with reporters. His remarks at events sometimes last nearly as long as hers. And he occasionally takes his own crack at answering a question that had been posed to her. (He often precedes his friendly interjection with “If I may …”)
It can at times look like a partnership, or even a presidential ticket. Ms. Haley regularly sings his praises — “How cool is your governor?” she asked in Rindge on Saturday — and Mr. Sununu usually tries to stay deferential.
“I’m no national figure,” he said in an interview. “When I walk into the room, all eyes are on her, as they should be. And she’s the star and she’s been great. I might know more people by first name, but they’re not there to see me.”
When Gov. Ron DeSantis of Florida dropped out of the race on Sunday and endorsed Donald J. Trump — becoming the second onetime rival to do so in recent days — Ms. Haley appeared increasingly isolated as prominent Republicans coalesced around the former president.
Except for Mr. Sununu.
“He’s putting his shoulder to the wheel, that’s for sure,” said Steve Duprey, a former Republican National Committee member from New Hampshire.
Mr. Sununu, a moderate political scion in the state who rarely appears in public without a wide grin on his face, is enjoying what seems to be the end — for now — of more than two years in the national spotlight.
Elected as governor in 2016, he first teased national Republicans with the prospect that he could flip one of his state’s two Senate seats in 2022, before choosing to run for governor again. Then he floated a 2024 presidential bid, garnering headlines and cable news specials. Without a foothold in polling or a clear path to victory, he decided against it.
For at least one more day, he is the most influential ally of Mr. Trump’s lone remaining Republican challenger. An upset victory by Ms. Haley in New Hampshire would burnish his standing among Republicans looking to move on from Mr. Trump. A loss by Ms. Haley, however, would be a further repudiation by Republican voters of the kind of conservatism Mr. Sununu preaches.
Mr. Sununu professes to be unworried about Mr. Trump’s lasting impact on the party.
“Trump is not a real Republican,” Mr. Sununu said in the interview. “Is he fiscally conservative? No. Does he believe in smaller government? No.”
Mr. Sununu seems content to end his intraparty crusade against Mr. Trump after he leaves office early next year: “My full plan is to go back into the private sector.” But he does not appear prepared for a total vanishing act.
“I like this media stuff,” he said in his interview with The New York Times, which was sandwiched among an appearance on NBC’s “Meet the Press,” a podcast hit and a Bloomberg interview in the span of 90 minutes. “I have my quiet criticisms on the media and I’ve gotten to see how they do it, what they do, how they work. And some things I’m impressed by. And some things I’m not. So I thought, oh, maybe I could add a little bit of color to what the media is currently doing and maybe enhance that game.”
Even if Ms. Haley is humbled on Tuesday, Mr. Sununu may not be done with electoral politics.
“He took her from Triple-A to major-league three or four weeks ago when he endorsed,” said Mike Murphy, a Republican strategist who has run many primary campaigns through New Hampshire, including former Senator John McCain’s bid in 2000. “He’ll leave office a very successful, multiterm governor. You’ll have a lot of New Hampshire offers. You know, they wanted him for Senate last time. They can always want him another time.”
Mr. Sununu’s endorsement of Ms. Haley in December was a major moment for her in New Hampshire, where Mr. Trump has led polls but appeared more vulnerable. And it has given the governor a taste of the limelight that he would have experienced if he ran himself.
“It’s like fantasy football,” said Thomas D. Rath, a former state attorney general and a longtime Republican strategist. “I think part of him really wanted to try the bigger game, but I think he was realistic enough to say that’s not going to work. So this is probably the next best thing.”
Mr. Sununu insisted that he had no regrets about not running. “I definitely more than scratched the itch and it’s not for me, it’s really not,” he said. “It’s not for my family.”
But he has eagerly jumped into Ms. Haley’s campaign.
While she has generally avoided reporters’ questions, Mr. Sununu rarely bats away any. “Nobody cares,” was his response to a shouted question about Senator Tim Scott’s endorsement of Mr. Trump, before the Haley campaign had commented publicly.
He spent part of Saturday as chauffeur, driving Ms. Haley to a Chick-fil-A in Nashua in his red 1966 Ford Mustang convertible, though the top was up amid snow flurries.
Mr. Sununu has rarely met a voter he will not engage. At a diner in Amherst, he discussed teenage vernacular with Griselle Maya, 41, of Merrimack.
“My kid just says, ‘Brahh,’ for entire sentences, and the tone of the ‘brah’ is how you’re supposed to interpret what he means,” Mr. Sununu said with a chuckle. Ms. Maya, sitting with her daughter, laughed in agreement.
Ms. Maya said she was a big fan of his. She remained undecided on Ms. Haley.
Mr. Sununu’s personal feed on X, formerly Twitter, is a waterfall of pro-Haley propaganda, like a Swiftie whose only era is “Nikki Haley for President.”
The two share many mutual interests — “we’re both ’80s and ’90s kids,” he said — including a love of rock music. Ms. Haley has expressed admiration of Mr. Sununu’s entrance song, “Welcome to the Jungle” by Guns N’ Roses.
Of course, his full-throated support for Ms. Haley has drawn the ire of a particularly powerful and vengeful member of the Republican Party.
“I think your governor sucks,” Mr. Trump told a crowd on Friday. He added: “He was on every show, this guy. He thinks he’s hot stuff. He’s nothing. He’s nothing.”
Monica Burns, 78, a retiree from Brentwood, N.H., and an independent voter who supports Mr. Trump, said she had been put off by Mr. Sununu’s endorsement of Ms. Haley and his attitude toward the former president.
“I’m not happy,” Ms. Burns said. “I don’t think he’s ever been a Trumper. And so that really rubs me the wrong way. He’s been a decent governor, no doubt, but it really bothers me that he’s not for Trump.”
Mr. Sununu, whose approval ratings remain high, shrugs off such criticism.
“My sense is when he’s kind of off that national stage,” he said, “we can get back to actually good government again.”
Michael Gold contributed reporting from Concord and Portsmouth, N.H., Anjali Huynh from Hooksett, N.H., and Neil Vigdor from Kingston, N.H.