Ted Cruz is surging in the polls. Donald Trump is not happy.

Ted Cruz is surging in the polls, and Donald Trump is getting antsy about it.

Cruz vaulted ahead of Trump in the most recent Des Moines Register poll in Iowa, and he’s nipping at his heels in the latest national NBC News/Wall Street Journal poll.

With Trump’s anti-Muslim crusade doing absolutely nothing to diminish his popularity, Cruz is solidifying his position as the alternative or “toned-down” Trump—just as (and more consistently) hard-line conservative, but slightly less prone to say things like “all Muslims should be banned from entering the United States.” Though he’s said negative things about Trump in private, he’s refused to criticize him in public, hoping that Trump supporters will support him too, especially if Trump eventually gets pushed out of the race.

Trump has responded to this newly ascendant Cruz in typically bombastic fashion—mostly by noting that seemingly everyone who has ever known Ted Cruz hates him.

“I don’t think he’s qualified to be president,” he told Fox News on Sunday, according to Politico.  “I don’t think he has the right temperament. I don’t think he’s got the right judgment. … [Y]ou look at the way he’s dealt with the Senate, where he goes in there like a — you know, frankly like a little bit of a maniac. You’re never going to get things done that way.”

Cruz and Trump will meet at the next Republican debate in Las Vegas on Tuesday.