Former Senator and Republican commentator Scott Brown endorses Donald Trump for the Republican presidential nomination, as the candidates prepare for the New Hampshire primary (Reuters)

MILFORD, N.H. — Former Massachusetts senator Scott P. Brown, a moderate Republican who two years ago ran for Senate in New Hampshire, will endorse Donald Trump at a rally here Tuesday night, one week before the state’s presidential primary.

Brown’s decision has been closely guarded for days, but it was confirmed by two people familiar with the event, where Brown will appear onstage with the candidate.

When reached early Tuesday afternoon, the Trump campaign’s spokesperson would not discuss the rally or possible guests. Brown was unavailable for comment.

Brown’s move could give Trump a significant boost one day after the mogul lost the Iowa caucuses to Sen. Ted Cruz of Texas.

Although Brown was defeated in his senatorial bid here, he has been a popular GOP figure in New England ever since his stunning, come-from-behind victory in Massachusetts’s special election to fill the Senate seat in 2010.

Brown is also a favorite of many establishment Republicans because of his centrist positions, including support for abortion rights and for a ban on assault weapons. His profile and personality, however, are blue collar and populist. He drove a pickup truck during his Senate bids and is a habitué of Cheap Trick concerts.

On the endorsement front, Brown is the first U.S. senator, current or former, to formally back Trump.

In the New Hampshire contest, Trump faces stiff competition not only from Cruz but from a crowd of mainstream Republicans who have strong pockets of support in and have been relentlessly campaigning in the state, such as New Jersey Gov. Chris Christie, Ohio Gov. John Kasich and former Florida governor Jeb Bush. Sen. Marco Rubio of Florida, who placed a strong third in Iowa, is another threat.

The relationship between Trump and Brown has grown cozy in recent months with a series of meetings and phone calls. At a January event in Portsmouth, N.H., Trump said Brown was cut out of “central casting” and could be his vice-presidential pick. Brown called Trump “the next president of the United States.”

Speaking with reporters after the event, Brown said he was weighing three factors as he decided whom to endorse: “Somebody who is not afraid to make a decision and doesn’t always follow the polls; sometimes who will be politically incorrect and will do what’s best for this country. ... Someone also who is not afraid to admit when they’re wrong.”

That somebody is Trump.