Judge Jeanine: Mr. President, Let FBI Director James Comey Do His Job

Gutfeld: Fight Radical Islam With 'Radical Americanism'

On "Fox News Sunday," Republican presidential candidate described Donald Trump sniped at rival GOP candidate Sen. Ted Cruz, calling him "a little bit of a maniac."

Trump said he didn't think the Texas senator was qualified to be president, saying he lacked proper judgment and temperament.

When Chris Wallace pushed him to elaborate, Trump said it's about how he's acted on the Senate floor.

"When you look at the way he's dealt with the Senate, where he goes in there like a -- you know, frankly, like a bit of a maniac," Trump said.  "You never get things done that way ... You can't walk into the Senate and scream and call people liars and not be able to cajole and get along with people. 

"He'll never get anything done.  And that's the problem with Ted."

The billionaire business magnate had harsher words for Democrat Hillary Clinton, who he hit back against for saying he was dangerous. Trump said she was "one of the worst secretaries of state in the history of the country."

"She talks about me being dangerous," Trump said. "She's killed hundreds of thousands of people with her stupidity."

When asked to elaborate, Trump said to look at the Middle East, saying it was a "total disaster under her."

Watch the full interview above.

Ted Cruz Is Beating Donald Trump in the Latest Iowa Polls

Kurt Russell: 'Absolutely Insane' to Think Gun Control Will Stop Terrorists

Carson Threatens to Leave GOP: 'I Don't Want to Be a Part of Corruption'