"I don't think he's got the right temperament. I don't think he's got the right judgment," Trump told host Chris Wallace. "You look at the way that he's dealt with the Senate, where he goes in there, frankly like a little bit of a maniac. You're never going to get things done that way."

The conservative radio host focused on a "Fox News Sunday" interview during which Trump suggested Cruz couldn't work with others to get things done in Congress.

Limbaugh said on his show Monday that "even people who are not particularly aligned with Cruz on the right have gotta be curious about this because this is no different than what the media would say about Ted Cruz. This is no different than what the Democrat Party would say."

"I mean, this is what the Republican establishment would say, for crying out loud. I mean, this is akin to saying, 'I'm the guy who can cross the aisle and work with the other side.' That hasn't been the way Trump has come off up 'til now. He's not positioned that way," Limbaugh said.

"He's essentially put on his John McCain hat here and is saying, 'I'm Donald McCain, and I'm the guy that can cross the aisle and work with the other side. Ted Cruz can't.' I was kind of surprised by that," Limbaugh added later.

Cruz has picked up steam in the early voting state of Iowa, where he now leads Trump, according to a Des Moines Register/Bloomberg poll released over the weekend. Cruz, who has largely avoided publicly attacking Trump while other GOP rivals have slammed the businessman, responded with humor to Trump's "maniac" remark on Sunday.

Later in his show, Limbaugh – who lauded Cruz as being "just brilliant in the way he's been behaving" during the campaign and said Cruz has now "forced Trump into a couple of major blunders" – suggested the latest attack was "so unlike Trump" and a "huge mistake."