Transcript for Battle Heats Up Between Trump and Cruz
The reaction is coming in from the campaign trail. Thankful they are coming home. And among the republicans, agreement the nuclear deal is a that's V disaster for America and a victory for Iran. There are other sharp words on campaign trail tonight. The love fest between Ted Cruz and Donald Trump appears to be officially over. Here's Mary Bruce. Reporter: Tonight, the front-runner slug fest escalating. Donald Trump and Ted Cruz hurling jabs across the key states. The day started with a flurry of tweets with Donald Trump blasting his former friend. Over Cruz's eligibility to be president. Ted Cruz was born in Canada and was a Canadian citizen until 15 months ago. Lawsuits have been filed. I told you so. Cruz fires back. It seems Donald has a lot offer in energy. Donald doesn't react when he is doing down in the polls. Reporter: And when he got stuck in the elevator -- So who put Donald Trump in charge of the elevators? In New Hampshire, trump unloaded on the Texas senator, questioning two undisclosed loans Cruz made in his senate run. He went off the wagon a little bit and went a little crazy. I mean, he is being a great hypocrite. Reporter: And his crews took the stage in South Carolina, more tweets, trump slamming Cruz for his comments on New York value. Asking, is this the New York that Ted Cruz is talking about and demeaning? Hello, everybody. Reporter: Trump following Cruz at the same event and not letting up. Actually, New York has had very high values. Reporter: And tonight, the democratic race is also coming here to South Carolina. Just as the race is tightening, Clinton and sanders are attending the same dinner tonight before facing off tomorrow in a debate, the last one before the Iowa caucuses.
This transcript has been automatically generated and may not be 100% accurate.