Governor Chris Christie on Friday endorsed his former rival Donald Trump for the presidency, adding another stunning development to a race for the White House that has surprised at nearly every turn.

The New Jersey governor gave Trump his backing during a press conference before a rally in Fort Worth, Texas, in a joint appearance that was kept secret until Christie appeared before the cameras. “There is no better fighter than Donald Trump, and he’s going to fight for the American people,” Christie said. Trump, he said, was “rewriting the playbook of American politics” and was the strongest Republican candidate “to take on the D.C. establishment.”

For Trump, the endorsement materialized like a life raft on what was arguably the worst day of his campaign for president. Senator Marco Rubio landed numerous rhetorical blows on the front-runner during Thursday night’s debate and followed it up with a bravado performance at a campaign rally Friday, where he assumed Trump’s bullying persona to mock him for misspelling tweets, applying makeup to his sweating upper lip, and for demanding a full-length mirror to, in Rubio’s words, “make sure his pants weren't wet.”

By endorsing Trump, Christie may be angering Republican Party big-wigs who are desperately trying to stop the billionaire’s march to the nomination. But he is undoubtedly Trump’s biggest “establishment” get to date, and as Rubio’s former nemesis on the debate stage, the timing of his endorsement could not be more advantageous. Standing alongside Trump, Christie immediately got to work trying to cut Rubio down once again. “Desperate people do desperate things,” Christie said of the barrage that Rubio hurled at Trump on Thursday and Friday. And he attacked his lack of experience and his frequent absences from the Capitol during his single term as a Florida senator. Rubio, Christie said, “has shown himself over a period of time to be wholly unprepared to be president of the United States.”

Trump laid into Rubio in his own characteristic fashion as well. “I watched a part of his little act, and he’s a desperate guy,” he said. “He is a nervous nelly.”

“I have never seen a human being sweat like this man sweats,” Trump added, saying that Rubio was also applying makeup “with a trowel” backstage at the debate. And he reminded reporters of the “epic meltdown” Rubio suffered at the hands of Christie, when he began repeating talking points during a debate earlier this month in New Hampshire. “Once a choker, always a choker,” Trump said.

As for why he chose Trump to endorse, Christie cited a long friendship between their families and said he would be the strongest Republican to go up against Hillary Clinton in the fall. He made little mention of the many criticisms he leveled at Trump when he was a candidate, such as when he called Trump’s proposal to ban Muslims from entering the United States “ridiculous.” Yet the immediate question is what might he get for his endorsement? Trump was asked whether he’d be a candidate to be his running mate. “I don’t want to discuss that, but he’s certainly got the talent,” the front-runner replied.