President Donald Trump slammed Arizona Republican Sen. Jeff Flake on Twitter on Sunday evening, calling his political career "toast" after he was caught on mic criticizing the President and Alabama Republican Senate candidate Roy Moore at an event on Friday.
Flake was hosting a town hall event at aerospace company GECO in Mesa, Arizona, and was fielding questions about the Republican tax reform plan and a possible 2020 run against Trump when the incident occurred.
After an hour of discussion, Flake stepped off the stage without removing the microphone on his lapel, which was still feeding to the TV cameras in the back of the room.
While speaking to Mesa Mayor John Giles, Flake said if the GOP becomes "the party of Roy Moore and Donald Trump, we are toast."
Trump hit back Sunday using the senator's own words, tweeting, "Sen. Jeff Flake(y)" will "be a NO on tax cuts because his political career anyway is 'toast.'"
Flake's office responded late Sunday to Trump's assertion that he would vote against the GOP tax bill.
"Senator Flake is still reviewing the tax reform bill on its merits," his spokesman, Jason Samuels, told CNN. "How he votes on it will have nothing to do with the President."
The latest dust-up between the two comes as Republicans try to hold onto every vote as they push to pass the GOP's tax plan. The House passed their version of the legislation along party lines last week. But the prospects for the measure are more unclear in the Senate, where Republicans hold a slim two-seat majority.
Wisconsin GOP Sen. Ron Johnson has said he opposes the current Senate version, but has said he wants to negotiate changes in order to support the bill, and a handful of other Republican senators -- including Flake and Susan Collins, of Maine -- have raised concerns.
Flake told CNN last month that he wasn't going to vote for just any tax bill if he thought it was fiscally irresponsible.
Collins said on CNN's "State of the Union" on Sunday that a repeal of the Obamacare individual mandate that senators have included in the bill should be removed. She added that she thought more could be done in the legislation to help those earning lower and middle incomes.
"It benefits people of all tax brackets, but what I want to do is to skew more of that relief to middle- and low-income families," Collins told anchor Jake Tapper.
Republican leaders have vowed to get a tax bill to the President's desk by the end of the year.
Flake was critical of Trump during the 2016 campaign and has clashed with the President regularly over the past year, criticisms he wrote about in his book, "Conscience of a Conservative."
The senator announced last month that he would not run for reelection next year, delivering a blistering speech on the Senate floor that bemoaned the "coarsening" tenor of politics in the United States.
In the speech, Flake denounced the "complicity" of his own party in what he called an "alarming and dangerous state of affairs" under Trump, blaming the President for setting the tone. In his speech, Flake assailed a "flagrant disregard for truth or decency" and attacked a "regular and casual undermining of our democratic norms."
Flake's political fortunes suffered as a result of his long-running feud with Trump. Private polls conducted by Republican and Democratic groups in Arizona, sources with those groups said, showed him on track to lose badly in next August's Republican primary to challenger Kelli Ward.