Republican presidential candidates have been competing for Gov. Chris Sununu’s endorsement for months.Now, sources tell WMUR that Sununu has made his decision. He’s going to be backing former United Nations Ambassador Nikki Haley, and he will be making this endorsement official Tuesday night at a town hall event for Haley in Manchester.After declining to run for president himself, Sununu spent the summer and fall on the campaign trail with various candidates, looking for the one he felt would be best positioned to take on former President Donald Trump in the Republican primary.>> Download the free WMUR app to get updates on the go: Apple | Google Play < Republican presidential candidates have been competing for Gov. Chris Sununu’s endorsement for months. Now, sources tell WMUR that Sununu has made his decision. He’s going to be backing former United Nations Ambassador Nikki Haley, and he will be making this endorsement official Tuesday night at a town hall event for Haley in Manchester. After declining to run for president himself, Sununu spent the summer and fall on the campaign trail with various candidates, looking for the one he felt would be best positioned to take on former President Donald Trump in the Republican primary. >> Download the free WMUR app to get updates on the go: Apple | Google Play << Sununu has said he does not think Trump can win next year and wants the Republican Party to turn the page. Since September, the governor has spent the most time on the trail with Haley, Florida Gov. Ron DeSantis and former New Jersey Gov. Chris Christie. From what the governor has already said about how he plans to approach this, we’re going to be seeing him really put his popularity and political clout behind his chosen candidate, Haley. Sununu has consistently been one of the most popular governors in the country. Through three reelection bids, he has demonstrated a strong connection with New Hampshire’s swing, undeclared voters who are expected to play a key role once again in this primary. Sununu has previously said we’re going to see him really campaign for his candidate and try to begin a new era in the GOP to move on from Trump. Whether that’s what the Republican base wants remains to be seen, but for Haley, who has been steadily building momentum in New Hampshire, this could be the fuel she needs for another boost in the polls that puts her basically in position for a one-on-one contest with Trump in the home stretch. Trump will be in Durham for a campaign event on Saturday and it remains to be seen how he will respond to the news of Sununu’s endorsement. Another big question is how Christie will respond. Christie is all in on New Hampshire, but now the state’s most popular Republican has chosen his chief rival for the bloc of non-Trump Republican votes. It could cause him to lose some support. Endorsements, though, have become very hit-or-miss in modern politics. What we know for sure is Sununu is going to really try to make this one count.