By Doina Chiacu and Sarah N. Lynch
WASHINGTON (Reuters) - Republican presidential front-runner Donald Trump had a new target on Sunday, calling fellow White House contender Ted Cruz "a little bit of a maniac" as the U.S. senator passed him in an Iowa opinion poll.
Cruz's dogged pursuit of conservative Iowa voters has paid off in the form of a 10-percentage-point lead over Trump in the state, where the first presidential nominating contest will take place on Feb. 1.
Unlike the other Republicans seeking their party's nomination for the November 2016 presidential election, the U.S. senator from Texas has embraced Trump and avoided publicly criticizing the popular candidate.
But last week, he questioned Trump's judgment at a private fundraiser, according to the New York Times, after the billionaire developer advocated temporarily banning Muslims from entering the United States.
That got Trump's attention.
"I don’t think he is qualified to be president," Trump said on "Fox News Sunday."
"I don't think he has the right temperament. I don't think he's got the right judgment. When you look at the way he has dealt with the Senate, where he goes in there like a, you know, frankly, like a little bit of a maniac - you are never going to get things done that way."
Trump touted his ability to get along with liberals and conservatives and said that was the hallmark of the "world-class businessman" he is.
Cruz had a lighthearted response to the "maniac" label on Twitter later on Sunday, posting a link to a video clip from the 1983 film "Flashdance" showing star Jennifer Beals dancing energetically as the hit song "Maniac" plays on the soundtrack.
"In honor of my friend @realDonaldTrump and good-hearted #Maniacs everywhere," Cruz said in his tweet.
'HE'S BEEN SO NICE TO ME'
Trump, whose comments on Muslims have drawn widespread criticism but may not dent his lead in several national opinion polls, made a sarcastic reference to Cruz's respectful treatment of him.
"He's been so nice to me. I mean I could be saying anything and he'd say, I agree I agree," Trump said on CNN's "State of the Union."
On the Fox program, he also criticized Cruz for talking about him behind his back.
Cruz rose to 31 percent, above Trump's 21 percent, in an Iowa poll released on Saturday by the Des Moines Register and Bloomberg News. That is a 21-point jump from October.
His rise came at the expense of retired neurosurgeon Ben Carson, who dropped to third with 13 percent in the poll, while U.S. Senator Marco Rubio of Florida hovered at 10 percent. Former Florida Governor Jeb Bush was at 6 percent, a 1-percentage-point increase from October.
Rubio, who has seen an uptick in his own poll standings in recent weeks, criticized his Senate colleague on defense spending, saying Cruz talked about carpet-bombing Islamic State while voting to cut the military budget.
Rubio was measured in his criticism of Trump on NBC's "Meet the Press," saying: "There's a lot we have a difference of opinion on, but we can't ignore that he's touched on some issues that people are concerned about."
Trump made the same point on Sunday, saying Americans were living in fear of being attacked. He linked his proposal to ban Muslims temporarily to his tough-on-immigration ideas, which included building a wall at the border with Mexico.
"One of the reasons I'm sitting here and one of the reasons I'm so high in the polls is because it all started with the borders," Trump told CNN. "I took much more heat when I said illegal immigration and southern borders and the wall and all of that than I ever took for this."
(Additional reporting by Kevin Krolicki and Jonathan Oatis; Writing by Doina Chiacu; Editing by Alan Crosby and Peter Cooney)