Sen. Mitt Romney (R-UT) on Sunday claimed that former President Donald Trump’s refusal to show up at the GOP presidential debates was because the former president was scared of former GOP New Jersey gov. Chris Christie.

Romney made the claim in a Sunday interview on NBC’s “Meet the Press.” The lawmaker told host Kristen Welker that he would not be supporting the former president’s reelection bid.

“I’m not gonna be endorsing President Trump, obviously. I’ve made that very clear. Look, Chris Christie has done a terrific job so far,” Romney said. “I think his being in the race has kept Donald Trump from coming to the debates because I think Donald Trump recognized if he went to the debate with Chris Christie, Chris Christie would reveal him for what he was. And Trump would be badly hurt. So he stayed out.”

Romney, however, added that former South Carolina GOP Gov. Nikki Haley has the best chance of taking Trump down.

Nikki Haley, she’s rising. Right now, I think she’s the only one that has a shot at becoming the nominee other than President Trump,” Romney added. “It’s a long shot on her part, but she’s the one that has a shot. So we’ll see.”

The lawmaker said he would not be endorsing any of the candidates because his endorsement will hurt more than help.

“Well, because if I endorse someone it would be the kiss of death,” Romney responded when Welker asked why he has not endorsed anyone. “Should I endorse the person I like least right now?”

Romney, however, maintains that Trump would still be the favorite to become the GOP’s nominee for 2024 even if the other candidates consolidate behind one person.

Romney, who recently announced he won’t be running for his Senate seat next year, previously suggested that he would vote for a Democrat over Trump.

“I’d be happy to vote for a number of the Democrats, too,” he continued. “It would be an upgrade, in my opinion, from Donald Trump and perhaps also from Joe Biden.”