Before his rally in Phoenix on Tuesday night, President Trump met with potential candidates gunning for Sen. Jeff Flake's seat.

The president spoke backstage with state treasurer Jeff DeWit and former state GOP chairman Robert Graham, according to a Politico report. Both are considering a run in the Republican primary against Flake, who is up for re-election in 2018.

During the rally, Trump alluded to Flake, saying "weak on borders, weak on crime," an adage he has used to describe Flake in the past. Last week, the president tweeted: "Great to see that Dr. Kelli Ward is running against Flake, who is WEAK on borders, crime and a non-factor in Senate. He's toxic!"

Wednesday morning, Trump attacked Flake by name, tweeting, "Not a fan of Jeff Flake, weak on crime & border!" Flake later said he plans to ignore Trump's personal attacks and will remain "focused" on doing his job.

The Arizona Republican has been critical of Trump's agenda. His recent book, Conscience of a Conservative is a scathing critique of the 2016 election and Trump.

According to the report, Trump tore into the Flake during the short meeting, calling him "the flake." Trump also discussed a primary challenge to the Arizona senator. He told DeWit and Graham to get back to him about their interest in mounting a primary challenge.

Graham's daughter posted a picture of the meeting on Instagram.

Last tribute to the President of the United States, and my amazing father! What a wonderful picture in action!A post shared by *Faith Graham* (@faithywaithy707) on Aug 23, 2017 at 12:24pm PDT