(AP)
Ted Cruz and Donald Trump.

Donald Trump has a new target: Sen. Ted Cruz (R-Texas).

In multiple interviews Sunday, Trump took aim at Cruz. He said the senator's tactics in Congress had demonstrated that he would be incapable of driving the legislative agenda from the White House, and at one point called Cruz a "little bit of a maniac."

"I don't think he's qualified to be president," Trump told Fox News' Chris Wallace in a pretaped interview that aired on Sunday. "Look at the way he's dealt with the Senate, where he goes in there — like, you know, frankly, like a little bit of a maniac. You're never going to get things done that way."

In an interview on CNN, Trump added: "I actually get along with people much better than he does. You know people don't know that about me: I actually have a great relationship with people."

Trump has become increasingly willing to jab at Cruz amid his surge in polls, where he is challenging Trump's status as the front-runner in the influential first-caucus state of Iowa.

At a rally on Friday night in the Hawkeye state, the real-estate mogul contrasted Cruz's religious beliefs with his own "evangelical" beliefs.

"I am an evangelical. I'm a Christian. I'm a Presbyterian," Trump said.

"We're doing really well with the evangelicals. And by the way, and again, I do like Ted Cruz, but not a lot of evangelicals come out of Cuba, in all fairness. It's true. Not a lot come out. But I like him nevertheless."

Cruz, who has pledged to refrain from attacking his Republican opponents directly, has offered few criticisms of Trump's proposals on the campaign trail.

But behind closed doors, Cruz has attempted to contrast himself with Trump. The New York Times reported last week that at a recent Manhattan fundraiser, Cruz questioned Trump's "judgment" on foreign-policy and national-security issues.

"You look at Paris, you look at San Bernardino, it's given a seriousness to this race, that people are looking for: Who is prepared to be a commander in chief? Who understands the threats we face?" Cruz said, according to The Times. "Who am I comfortable having their finger on the button? Now that's a question of strength, but it's also a question of judgment. And I think that is a question that is a challenging question for both of them."

Cruz immediately looked to bury the hatchet on Friday, offering praise for the real-estate mogul in a tweet that was retweeted by Trump:

Part of Cruz's coziness with Trump's campaign appears be a political calculation. Cruz has said repeatedly that Trump's rise is "beneficial" and "helpful" to his own campaign, because Trump his whipped up antiestablishment fervor among conservatives that Cruz believes he also taps into.