Who will popular New Hampshire governor, Chris Sununu, endorse in the Republican presidential primary, and could that endorsement help catapult one of the second-tier candidates to victory over President Trump?

That was the main question Monday, when Mr. Sununu joined presidential hopeful, former South Carolina governor and United Nations ambassador, Nikki Haley at a campaign event in the Granite State. When an audience member shouted out “endorsement” as Mr. Sununu gave his opening remarks, the New Hampshire governor cracked a joke instead of making a formal commitment.

“I endorse New Balance wholeheartedly without a doubt,” Mr. Sununu said, pointing to his sneakers. He had just returned from an event celebrating the groundbreaking of a New Balance sneaker factory in Londonderry.

To reporters after the event, Mr. Sununu refused to give a timeline for his endorsement but said he is deciding between the three governors in the race: Ms. Haley, Ron DeSantis, and Chris Christie. “I get along with all of them. They’re all friends,” he said.

Ms. Haley is surging in the polls and has positioned herself as the moderate, more electable alternative to Mr. Trump. The latest Washington Post/Monmouth University poll shows Ms. Haley in second place in New Hampshire with 18 percent support — still far behind Mr. Trump, who is polling at 46 percent. Mr. Christie is in third with 11 percent, and Mr. DeSantis trails Vivek Ramaswamy with 7 percent.

The New Hampshire first-in-the-nation primary is scheduled for January 23, nine weeks away. Mr. Sununu said that is plenty of time to sway voters, and he indicated that his endorsement will come after Thanksgiving. He said once he does endorse, he will campaign for that candidate with “110 percent” effort.

Mr. Sununu knows how to win in the Granite State. He won reelection to a fourth two-year term as governor in 2022 by more than 15 percentage points. A critic of Mr. Trump, Mr. Sununu declined to run for president earlier this year because he said a large field would only increase the chances of Mr. Trump winning the nomination.

“As folks make up their mind in New Hampshire, I’ll start making up mine,” Mr. Sununu said.

Ms. Haley is having a campaign moment. The Wall Street Journal reported that Wall Street bankers looking for an alternative to Mr. Trump are now eyeing Ms. Haley as the best shot. Former Trump adviser Gary Cohn recently co-hosted a $10,000 per person fundraiser for Ms. Haley.

Ms. Haley is also surging in Iowa. She is tied with Mr. DeSantis in the latest Des Moines Register poll, though both still trail Mr. Trump by 27 percentage points. Iowa’s governor, Kim Reynolds, recently endorsed Mr. DeSantis.

About half the crowd at the packed event in New Hampshire Monday raised their hands when asked if this was their first Haley campaign event. The Sun spoke with several attendees, most of whom said they were looking for an alternative to Mr. Trump.

“Trump scares me. I absolutely would not vote for him,” a Granite State realtor, Kathy Sutherland, tells the Sun. “I watched Nikki Haley on the last debate and she intrigued me.”

Ms. Sutherland says she usually votes Democrat, but she is worried about the economy, the housing market, and high interest rates for home buyers. She is also concerned about President Biden’s age. “I do like Biden but I am concerned, like where is he going to be four years from now?” she said.

Several other attendees said they would consider voting for Mr. Christie, but not for Mr. Trump. Three attendees said if it comes to another Trump-Biden matchup, they would consider voting for Joe Manchin or another No Labels candidate.

Ms. Haley stuck to her stump speech at the event. She spoke about excessive spending in Washington, the struggles of the middle class, and floundering student test scores. She also spoke about the importance of securing the southern border, the threat from China, and the importance of American aid to the wars in Ukraine and Israel.

She recycled her usual applause lines: “The Senate is the most privileged nursing home in the country,” Ms. Haley said. “I didn’t pull a Kamala and go and come back,” she joked about visiting the border.

One topic that Ms. Haley did not touch was abortion. She has positioned herself in the Republican presidential debates as “unapologetically pro-life,” but has urged Republicans to stop “demonizing” the issue and to “find consensus” on limits. Republicans lost in the 2022 and 2023 elections on the issue of abortion.

On Friday, though, in front of a group of Christians in Iowa, Ms. Haley broke from her usual stance and said she would have signed a 6-week abortion ban as South Carolina governor if the bill crossed her desk. The Biden campaign was quick to pounce.

“Nikki Haley is no moderate – she’s an anti-abortion MAGA extremist who wants to rip away women’s freedoms just like she did when she was South Carolina governor,” the Biden-Harris campaign said in a statement.

Ms. Haley is polling well against Mr. Biden, but her pitch as the more electable Republican candidate is losing some weight as Mr. Trump is now beating Mr. Biden in recent polls. This more extreme abortion stance from Ms. Haley could also affect her electability among moderates and independents. The Biden campaign would no doubt run a clip of her recent Iowa response in ads if she wins the Republican nomination.

For now, though, the biggest hurdle for Ms. Haley and the other governors Mr. Sununu is considering endorsing is overcoming Mr. Trump. If polling is accurate, that’s a big hurdle to jump.