Man. Lotta 2010-vintage tea-party heroes are climbing aboard the Trump train these days, huh? First Palin, now this. Presumably Trump’s holding the Joe the Plumber endorsement in reserve for just the right moment.

This is a decent get for Trump.

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 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 due to 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.

WaPo says Brown’s decision to back Trump has been “closely guarded” for days. Yeah? In that case, what was Brown doing two weeks ago at a Trump rally in New Hampshire introducing him as the next president of the United States? That’s not a compliment you’d lay on someone if you’re considering endorsing anyone else.

Erick Erickson snarks:

Touche, but congressional endorsements are hard for Trump to come by, especially now that he’s lost Iowa and isn’t the apparent juggernaut he looked to be 24 hours ago. Brown is likable, well known in the northeast, and media-friendly; he’s a good surrogate to have, especially to help Trump take some of the harder edges off his image. If I’m right that Trump’s main concern in New Hampshire right now is making sure no “Stop Trump” coalesces behind Rubio or Cruz, Brown is a valuable ally insofar as he embodies the centrist “reasonable Republican” stereotype. How much of a dangerous loose cannon could Trump really be if a nice, sober guy like Scott Brown digs him?

Trump said something a few weeks ago about how Brown is straight out of central casting as a potential VP. Yeah, I guess — except for geography. A Manhattanite and a New Englander would not make for a ticket that accurately represents the GOP base. That’s why I half-joked last week that Huckabee is better veep material for Trump. He’s from the Republican south, he has years of executive experience, and he can boast not only the same blue-collar cred as Brown but the social-conservative cred that Trump needs (especially after Iowa). Trump makes sense for Brown to endorse, though, because (especially as of two weeks ago) he looks like Brown’s fastest ticket back to relevance. He’s still the odds-on favorite to win New Hampshire, and he’s essentially a centrist independent masquerading as a Republican, just as Brown was. His support isn’t worth much to the establishment candidates in NH, all of whom have bigger names in their corner than Brown, but it’s worth something to Trump since it lends him some congressional legitimacy by association. If you’re looking for a path back into politics and you’re unwilling to accept a “demotion” from the Senate to a House seat (which is rough sledding in New England for any Republican, even with Brown’s fame), a longshot bet on Trump isn’t crazy.

One other interesting thing about Scott Brown: He’s a Romney guy, or at least he was. Romney helped him win the special election in Massachusetts in 2010. Brown repaid the kindness by endorsing Romney for the 2012 nomination. Romney hit the trail again for Brown in 2014, when he ran for Senate in New Hampshire. Now here’s Brown endorsing the one guy in the race (with the possible exception of Ted Cruz) whom Romney would least like to see succeed him as GOP nominee. Huh. I wonder if there’s been a falling out, or if Brown’s simply concluded that there’s no path back to office via traditional establishment means and so he needs to gamble with Trump. Either way, the spectacle of a Romney guy endorsing in New Hampshire raises the question again of when the man himself will speak up about the race. There’s little doubt now that Rubio will be the center-right champion against Trump and Cruz; if Romney doesn’t throw him his support this week, it’s probably only because he doesn’t want to kneecap Christie and Bush before New Hampshire voters render a verdict. Romney’s endorsement is worth something in New Hampshire, though, and Trump is still way ahead. If he wants to help Rubio make a dent in the polls there, now’s the time.

Here’s Brown not denying that he’ll make news at Trump’s rally in New Hampshire tonight.