New Hampshire’s popular Republican governor, Chris Sununu, plans to endorse Nikki Haley, according to WMUR, but will this endorsement be enough to catapult Ms. Haley to a win in the first-in-the-nation primary?

Mr. Sununu will be joining Ms. Haley at a town hall event in Manchester Tuesday evening, when he is expected to make the endorsement official. The New Hampshire primary will be held on January 23, just 6 weeks away.

The former South Carolina governor and ambassador to the United Nations has been gaining momentum the last few weeks after strong early debate performances and the endorsement of libertarian-conservative political advocacy group, Americans for Prosperity. Yet she is still trailing President Trump by more than 20 points in the Granite State, and by more than 30 points in Iowa.  

Mr. Sununu has been an outspoken critic of President Trump and declined to run for president this cycle because he said a large field would help Mr. Trump secure the nomination again. He said last month that he was mulling an endorsement of one of the three remaining governors in the race — Ms. Haley, Ron DeSantis or Chris Christie — and that once he endorsed he would put “110 percent” effort into the campaign.

“He’s ready to make his mark in granite, and it should be no surprise that it’s Nikki Haley,” a Republican strategist in New Hampshire and former Trump State Department appointee, Matthew Bartlett, tells the Sun. “Is it enough to win the game? Unclear. Will it change the game? Yeah, it’s gonna.”

Mr. Sununu is widely popular in the Granite State. He won reelection to his fourth two-year term as governor in 2022 by more than 15 points. A Washington Post-Monmouth University poll last month found that 81 percent of Republican and undeclared voters in the state approve of the job Mr. Sununu is doing.

“The trust and bond and the attention of the voters that have been with him for almost a decade will now absolutely be giving Nikki a good look,” Mr. Bartlett says. “He’s putting a very big flashlight on her.”

Yet that same Washington Post-Monmouth University poll also found that only 14 percent of likely Republican primary voters said Mr. Sununu’s endorsement would make them “more likely” to vote for a candidate. About 80 percent said it would make no difference.

Mr. Sununu told reporters he thinks a third of Mr. Trump’s supporters would be willing to switch their votes to another candidate. He also conceded to reporters last month that an endorsement is not a golden ticket — it’s the campaign help that comes with an endorsement that matters. He promised to help the candidate he endorses connect with town selectmen, school board members, and local leaders who helped him win in the state.

“The endorsement matters a little bit. The emphasis, the energy you put behind the campaign, the messaging — that’s really what matters and what’s going to get people galvanized,” Mr. Sununu said. “Believe me, I’ve been in this game long enough to know political momentum is real.”

Mr. Bartlett says Mr. Sununu’s endorsement of Ms. Haley is also a “significant setback and severe blow to team DeSantis.” Mr. Sununu campaigned with Mr. DeSantis several times in recent months. Mr. DeSantis is trailing Ms. Haley in Granite State polls, but he is beating her in Iowa. 

“Sources? I’ll believe it when I see it,” the New Hampshire house majority leader, Jason  Osborne, who has endorsed Mr. DeSantis, posted to X. “It would be an unfortunate development and a missed opportunity. The free state governors make a great team.”