Transcript for Trump Lashes Out At Carson While Clinton Plans Katy Perry Rally
the race for the white house. And Donald Trump lashing out over night at doctor Ben Carson who for the first time is leading trump in the polls in the key state of Iowa. Meanwhile, Hillary Clinton is on a roll and she is prepared to celebrate at a rally with Katy Perry. Good morning. Reporter: Good morning, a very good morning for Hillary Clinton. She is hitting the trail with benghazi behind her. And tonight, she parties with Katy Perry. Now benghazi is behind her, she is all smiles. I'm not running for bill Clinton's term. I'm running for my first term. Reporter: She turned it to her advantage. You going to be able to come to the Katy Perry concert? I hope so. I hope so too. Reporter: Three out of her path. Joe Biden stepped aside. Joe Webb dropped out of the democratic race. And now only did dernny sanders and mark O'Malley stand in the way for the nomination. The biggest question, what does Katy Perry open with tonight? "Roar" or "This is how we do." One thing for sure, it's not going to be "Dark horse." Meanwhile, the new republican front runner Iowa is spending his time signing books at Barnes & nobles in Missouri, Kansas, and Texas. Ben Carson is out on his book tour, letting a new campaign ad speak for them. Learning from crowds they are hungry for honesty and real solutions to the problems that ail us. Reporter: Donald Trump had this to say. He is super low energy. Super low energy. Reporter: That event in Miami was the first time that Donald Trump has gone off against Ben Carson, clearly driven by the polls and I guess it bothered him. The low energy comment is what he was using with Jeb bush for a while. Is there a sense in the republican hierarchy the dip in the polls in Iowa may be the beginning of the end for him? Some of them may be crossing their fingers and hoping so. But his end has been predicted many times. It has. And she is still strong in the national polls, worth pointing out. We will have more on the presidential race tomorrow morning right here on ABC with Donald Trump himself. Appears on ABC's "This week".
This transcript has been automatically generated and may not be 100% accurate.