In a stunning betrayal of the Republican establishment, and a crushing blow to Marco Rubio, New Jersey Gov. Chris Christie has endorsed Donald Trump for president.

Given Christie's relative lack of standing in the party, it may not win Trump the nomination by itself, but it is an enormous crack in the top party ranks, which were supposed to be closing around Marco Rubio right now. It signals that GOP elites may just throw in with Trump instead of trying to beat him.

Christie was a candidate for president himself, of course, who only dropped out about two weeks ago after finishing fifth in the New Hampshire primary. Dogged by corruption and the George Washington Bridge scandal, he was never much of a contender, but he famously trounced Rubio in his last debate. He repeatedly needled Rubio about his reliance on canned stump speech lines, to which Rubio responded by helplessly repeating his stump speech line again. It was extremely funny in a way that suggested, in line with other reporting, that Rubio may have a tendency to lock up and panic under moments of extreme pressure — a somewhat alarming characteristic in a potential president.

Given Rubio has promised to give up on his Florida Senate seat, losing this primary would probably be the end of his political career.

Now, it could be that Christie has simply given up on the Republican Party and is hoping that on the off chance that Trump wins, he will appoint him attorney general or something. But it's worth looking at this in the context of recent polls. Trump is simply dominating everywhere. His national lead is strengthening. The multiple primaries of Super Tuesday are coming up next week, and Trump is ahead in nearly every state. He's ahead by over 20 points in Florida, Rubio's home state. He even appears to be gaining on Ted Cruz in Texas. An overall poll of primary voters in those states found Trump winning overall, and winning head-to-head matchups with both Cruz and Rubio.

In short, Trump is winning this thing in a walk. He's not guaranteed victory by any means, but for him to lose from such a strong position would be literally unprecedented. Unless something extremely dramatic happens over the weekend, Trump is going to sweep the vast majority of delegates up for grabs on Tuesday, and the sheer pageantry of victory and ensuing media coverage is going to strengthen his lead still further.

Earlier today, Rubio was finally attacking Trump on something like his own level, making pee jokes and mocking Trump's spelling mistakes in his tweets (though he made his own goof in the process). But Christie's endorsement throws a gigantic wrench into what is almost the last opportunity for the Republican Party to stop Trump. It ensures that media coverage over the weekend will be consumed with more pro-Trump coverage. It's hard to imagine a worse development for Rubio.

And that, in turn, changes the calculus for other Republicans. It might be an idiosyncratic move from Christie, or it could be that he's the first one to see the writing on the wall.

If you cannot beat The Donald, perhaps best to join him.