New Hampshire Governor Chris Sununu Will Endorse Nikki Haley

Gov. Chris Sununu of New Hampshire is expected to endorse Nikki Haley for the Republican presidential nomination at a campaign event Tuesday evening, according to a source familiar with the plans.

The expected endorsement is significant for Ms. Haley, who is trying to establish herself over Gov. Ron DeSantis of Florida as the main alternative to former President Donald J. Trump and has risen a few points in the polls in New Hampshire in the past month.

WMUR first reported the news of the expected endorsement.

A spokesman for Mr. Sununu declined to comment but sent a statement from Mr. Sununu: “I look forward to joining Nikki at her town hall this evening — it’s going to be a lot of fun!”

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.

Given his popularity and his proven ability to win as a Republican in a state that leans Democratic, Mr. Sununu’s support could carry weight among 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. (Independent voters can participate in the Republican primary.)

But how much weight it will actually 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.

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.