Donald Trump meets with potential primary challengers to Arizona Sen. Jeff Flake. Instagram/faithywaithy707 President Donald Trump met with two potential challengers to a vulnerable Republican senator on Tuesday, reaffirming his baffling commitment to ousting a member of his own party from Washington.

The president has made no secret of his desire to replace Arizona Sen. Jeff Flake, who escalated his criticism of Trump in his new book "Conscience of a Conservative." On Tuesday, Trump briefly spoke with Arizona Treasurer Jeff DeWit and former state GOP Chairman Robert Graham, both of whom are considering challenging Flake in next year's Republican primary, according to Politico.

The brief meeting came backstage at the Phoenix Convention Center before Trump hosted a campaign-style rally. It also included GOP Rep. Trent Franks, a member of the House Freedom Caucus, Politico noted.

Trump reportedly gauged DeWit and Graham's interest in running against Flake, who he derisively referred to as "the flake," Politico reported.

During the rally that followed the meeting, Trump blasted Flake — "weak on borders, weak on crime," Trump said — while making a point of not calling the senator out by name.

"Nobody wants me to talk about your other senator, who's weak on borders, weak on crime, so I won't talk about him," Trump said, eliciting jeers from the crowd. "Nobody wants me to talk about him. Nobody knows who the hell he is. And now, see, I haven't mentioned any names. So now, everybody's happy."

Trump ditched any pretense of subtlety in a Wednesday-morning tweet:

Flake, while criticizing Trump's plan to build a wall on the US-Mexican border, has voted for Trump's position in 94% of the Senate votes this year, according to FiveThirtyEight.

Another Republican, former Arizona state Sen. Kelli Ward, has formally launched a bid to challenge Flake in 2018. Ward previously challenged Sen. John McCain for the Republican's seat in 2016.

Trump's assault on Flake, as well as other vulnerable Republican senators such as Dean Heller of Nevada, have angered members of the Republican leadership. A super PAC aligned with Senate Majority Leader Mitch McConnell released an attack ad on Tuesday painting Ward as a conspiracy theorist, The New York Times reported.