Transcript for Republicans Demand Apology After Donald Trump Slams John McCain

Donald Trump infuriating so many tonight, this time taking on a new target, John McCain, saying the Vietnam vet is no war hero. The reaction immediate and fierce. Nearly every single republican in the case pouncing, one demanding trump drop out. So far trump is not backing down, and ABC's Ron Claiborne starts us off tonight with this political firestorm. Reporter: At a candidates' forum in Iowa, Donald Trump at it again, this time ripping into senator John McCain. He's not a war hero. He's a war hero. He's a war hero because he was captured. I like people that weren't captured. Reporter: Those fiery remarks, retaliation from McCain accusing him of stoking crazies with his comments about illegal immigrants from Mexico. They're bringing crime. They're rapists. Reporter: Remarks that have helped Kalt put trump to the top of the poles. Now trump's attack on McCain and a Vietnam veteran who spent more than five years in a P.O.W. Camp has given them an opening to go after him. Donald Trump owes every American veteran, and in particular John McCain, an apology. That's just a disgrace. Reporter: Nearly every G.O.P. Contender weighing in today, many of them on Twitter. Jeb bush not mentioning trump by name but saying enough of the slanderous attacks. McCain's close friend Lindsey graham calling it a stupid statement. Even the republican national committee issuing a statement saying, there is no place in our party or our country for comments that disparage those who have served honorably. McCain's daughter Megan jumping in, tweeting horrified, disgusted, there are no words. Late today trump followed up with a new statement and not backing down, saying I am not a fan of John McCain because he has done so little for our veterans. For weeks his republican rivals have watched in horror but said very little as trump has dominated news coverage and risen in the poles. This attack on John McCain they now see an opportunity, and one provided by trump himself, to go after him. Tonight John McCain had no comment.

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