Ted Cruz Takes the Lead in Iowa Polls, Donald Trump Calls Him 'A Maniac'

Cruz's lead in back-to-back Iowa GOP polls could make him the target in Tuesday night's Republican presidential debate.
3:43 | 12/14/15

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Transcript for Ted Cruz Takes the Lead in Iowa Polls, Donald Trump Calls Him 'A Maniac'
The race for president now. The big shakeup as gop kptds get S set to face off tomorrow night. Ted cruise is surging in the polls. Closing in on Donald Trump nationally. Reporter: Good morning. One of the Iowa polls shows senator Cruz with a ten-point lead. Trump who usually loves the polls when he's winning, calling that poll biased towards him. He's still the front-runner nationally, as you can see. On the eve of the debate, the big story is Ted Cruz. This morning, a shakeup in the gop race for president. Back-to-back polls showing senator Ted Cruz now the man to beat in Iowa. Dornld trump not happy about it. You look at how he has dealt with the senate. He goes in there a little bit like a maniac. Reporter: Cruise reacting on social media. Posting a vivid Yo of the famous maniac dance scene. ? She's a maniac maniac at your love ? Reporter: But trump not laughing offer the audio of Cruz speaking behind closed doors with donors surfaced, questioning if trump was fit to be commander in chief. That's a question of strength. But it's also a question of judgment. Reporter: Trump striking back. Tweeting I was disappointed that Ted Cruz would speak behind my back, get caught. Cruz goes into the debate with target on his back. The only budge he's voted for is a budget that cut defense spending. Reporter: Over the weekend, "Snl" taking a look at the gop race with blast from the past. Rubio and Cruz, sounds like a Miami law firm. If you've been injured on the job, call Rubio and Cruz. Reporter: Will Ferrell reprising his role as George W. Bush. Jobing he is entering the race. They wnt someone who is cuckoo for cocoa puffs. Reporter: Controversy has been brewing. He took on the media and moderators. Tomorrow, we'll see if he take on trump. We're all going to be tuning in. We are. Let's talk to Jon Karl. Cruz really firming up his support. Yeah, the story of both of these new Iowa pols is Ted Cruz. He's surging. Jumping more than 20 points since October in that Des Moines register poll. While trump's Numbers have essentially remained the same. If you look deeper into the polls, you see Cruz has more potential to keep rising. Fox News poll, 30% say they would never vote for Donald Trump. Only 6% say they would never vote for Ted Cruz. The most unpopular republican in Iowa right now, is by far, Jeb bush. Ted Cruz is above 50% if you add up some of the Numbers. The last one before the christmas-new year's freeze. It is crucial. Once again. Donald Trump will be at center stage. George, five debates. All five, Donald Trump has been in the middle because he still has a commanding lead in the national polls. For the first time, Ted Cruz will be standing next to him. Because he has surpassed Marco Rubio in the pols. I'll be looking for how both trump and Marco rub ye go at Ted Cruz. He now in competition to be the alternative to Donald Trump. And Chris Christie back on the big stage as well.

This transcript has been automatically generated and may not be 100% accurate.

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