Transcript for 2 Republican senators take on Trump
We begin tonight with two leading senators taking on president trump. One of them standing on the floor of the senate late today saying I rise to say enough. Arizona's Jeff flake adding, I will not be complicit. It comes just hours after Republican senator Bob corker reignited his very public feud with the president. Corker calling the president, quote, an utterly untruthful president. President trump unleashing a Twitter attack, and tonight, the white house responding. ABC's Mary Bruce leading us off. Reporter: Standing on the senate floor, the Republican senator delivered an extraordinary indictment of the Republican president, calling Donald Trump "Reckless, outrageous and undignified." I rise today to say enough. Reporter: Arizona senator Jeff flake says he will not run for re-election, because he is so disgusted. The personal attacks, the threats against principles, freedoms and institution, the flagrant disregard for truth or decency, the reckless provocations, most often for the pettiest and most personal reasons. Reporter: And to his colleagues, a warning that, quote, "Silence can equal complicity." We have fooled ourselves for long enough that a pivot to governing is right around the corner, a return to civility and stability right behind it. We know better than that. Reporter: Calling it a matter of duty and conscience, flake now joins a wave of top Republicans ripping into the president. The morning, it was senator Bob corker, letting loose on "Gma." I would just like for him to leave it to the professionals for a while. Reporter: In response, the president unloaded in a barrage of tweets, claiming he "Refused to endorse" corker. Saying he "couldn't get elected dog catcher." And calling the influential head of the foreign relations committee a "Lightweight," "Incompetent," adding "People like little Bob corker have set the U.S. Way back." Corker, who has called the trump white house an adult day care center, tweeting back, "Same untruths from an utterly untruthful president. #Alertthedaycarestaff." He told reporters everyone sees through trump's bullying. And I think that the worst of it is going to be just the whole debasing, if you will, of our nation. Reporter: You think the president is debasing the nation? I don't think there's any question. Reporter: Corker was an early supporter of trump. But asked if he would do it again, he said, "No way." It all comes the same day the president traveled to the capitol to rally Republicans on tax reform. Mr. President, any comment on senator corker? Reporter: But his feuds are overshad doefing his agenda. Does any of this make the president pause and wonder if he is doing anything wrong? That he bears any responsibility? Look, I think the voters of these individual senators' states are speaking in pretty loud volumes. I think that they were not likely to be re-elected and I think that shows that the support is more behind this president than it is these two individuals. Let's get to Mary Bruce. And Mary, the white house says senators corker and flake are from states that voted for president trump. They're still around for awhile, and the president needs their votes, especially with his big push for tax reform. Reporter: Exactly, and David, a reminder of the math here. Senate Republicans have just a two-vote majority. Now, you have two top Republicans who don't feel the pressure of re-election, and aren't exactly inclined to just fall in line behd the president. But some Republicans are happy to see them go. A source close to Steve Bannon told ABC news his reaction tonight, another day, another scalp.
This transcript has been automatically generated and may not be 100% accurate.