Transcript for Donald Trump and Ted Cruz Slam Iran Nuclear Deal on Capitol Hill
So hard to drive and look both ways. Kayna, thanks. And to a new showdown in this country over Iran. Hillary Clinton making the case for the president's groundbreaking deal. Saying if elected, she wouldn't hesitate to use military force if Iran tried to get a weapon. Meanwhile, trump is sounding off. Jonathan Karl with trump tonight. Reporter: Mr. Trump goes to Washington. Hitting capitol hill to rally against the Iran nuclear deal. Never, ever, ever in my life have I seen any transaction so incompetently negotiated as our deal with Iran. Reporter: Light on specifics as usual, but heavier than usual on bravado. We will have so much winning if I get elected that you may get bored with winning. Reporter: While most of trump's gop rivals have been attacking him, today Ted Cruz, who invited trump to the rally, quite literally embraced him. Why Donald Trump? Why was Donald Trump here? Well, look, it is not complicated. Number one, I like Donald. But number two, everywhere Donald goes, he brings 100 television cameras. Reporter: While trump and Cruz hammered the Iran deal, across town Hillary Clinton praised it. Vowing to take the toughest of tough lines if Iran violates the deal. I will not hesitate to take military action if Iran attempts to obtain a nuclear weapon. Reporter: Big speech by Hillary Clinton today and she was really talking tough on Iran. She is trying to get the focus off her because she is a disaster. Honestly, Jonathan, if she doesn't, she is in big trouble I don't see how she goes to the starting gate. Reporter: The dwe debate on Iran formally started today in congress. But bottom line, in Arizona, fears of a possible serial shooter terror.
This transcript has been automatically generated and may not be 100% accurate.