New Hampshire Gov. Chris Sununu is expected to endorse Republican presidential candidate Nikki Haley Tuesday afternoon, according to sources familiar with the matter. 

Haley has been campaigning heavily in New Hampshire and has surged to second place in polling behind former President Donald Trump, though he's still maintaining a double-digit lead. Sununu, who has high approval ratings in his state, has been a vocal critic of the former president, though it's unclear how much impact his endorsement will have. 

Sununu is expected to announce his endorsement at an event with Haley in Manchester. 

"I look forward to joining Nikki at her town hall this evening — it's going to be a lot of fun," he said in a statement released by his office, though he did not confirm his intention to endorse her. 

Sununu has been campaigning with other Republican presidential candidates in New Hampshire, too, joining Florida Gov. Ron DeSantis and former New Jersey Gov. Chris Christie at their events. 

In November, Sununu appeared with Haley at several campaign stops and encouraged New Hampshire voters to engage with the Republican presidential candidates coming through their state before its first-in-the-nation primary in late January. 

"In this country, we're going to be back on top, and it all starts right here in New Hampshire, and whatever we can do to help these candidates — get them to where we want them to be, where the country wants them to be, ask them the right questions, get to know them as individuals," he said at one town hall with Haley in Hooksett. "It's an amazing opportunity we have." 

At one Londonderry event, Haley jokingly pressed Sununu for his backing.  

"Are you ready to endorse me?" Haley asked him at a town hall in a packed diner.

"Getting closer every day," Sununu replied. 

New Hampshire voters attending Haley's town halls often say that while they supported Trump in previous elections, they're searching for an alternative this time.

"I think that he was a great president when he was there," said Noel Searles, a New Hampshire retiree. "He did a lot of good things. I like the idea that Nikki Haley has a lot of the same policy views that he does, but I think that his arrogance right now is a detriment, and I'm not so sure that he's electable."

In:
• Chris Sununu
• Nikki Haley