President Trump and top administration officials are speaking with potential primary challengers to Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (R-Ariz.) amid frosty relations between the Republican president and the moderate GOP senator, Politico reported Monday.

Trump has personally talked to Arizona Treasurer Jeff DeWit, who worked on the Trump campaign, at least twice since taking office. Other administration officials have spoken with former state Sen. Kelli Ward and former Arizona GOP chairman Robert Graham, the report said.

Ward has announced her bid for Senate, while DeWit and Graham are considering campaigns. David Bossie, Trump’s deputy campaign manager, reportedly told Graham that he or DeWit would get significant support from conservatives if they launched campaigns.

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Flake, who is up for reelection in 2018, has been a top Republican critic of Trump, refusing to endorse him during the 2016 campaign. He said in June that he couldn't see himself voting for Trump.

A spokesman for Flake noted to Politico that Flake had “voted with President Trump over 95 percent of the time this year” and backed some of Trump’s biggest goals, such as Supreme Court Justice Neil Gorsuch’s confirmation.

Trump reportedly considered donating $10 million to defeat Flake in the 2018 primary.