Bob Corker, the Senate Foreign Relations Committee chairman, may face a Steve Bannon-backed challenger in 2018. AP Photo/J. Scott Applewhite

A Republican senator who was once on Donald Trump's short list for a Cabinet spot but has since feuded with the president could be targeted by a primary challenger backed by Steve Bannon.

Trump's former chief strategist is seeking primary challenges to several GOP senators, including Sen. Bob Corker, of Tennessee, the chair of the Senate Foreign Relations Committee, according to Politico and CNN.

Politico notes that Breitbart News published an article promoting a potential Corker challenger — state Sen. Mark Green — after Bannon returned to the right-wing site.

Also in Bannon's crosshairs are Sen. Dean Heller of Nevada, Sen. Jeff Flake of Arizona, and Sen. Roger Wicker of Mississippi, Politico and CNN reported.

CNN separately reported on Monday, however, that Corker, who is up for reelection in 2018, was thinking of retiring next year after two terms.

"As far as what am I going to do in the future, I'm still contemplating the future," Corker told CNN.

"It's a tremendous privilege to do what I do and to weigh in on the big issues," the senator said. "But I have not decided what I'm going to do in the future."

Trump tweeted in August that the Tennessee senator "is constantly asking me whether or not he should run again in '18."

That tweet came a week after Corker offered some sharp criticism of the president at a town hall in Tennessee.

"The president has not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate in order to be successful," Corker said of Trump’s response to the violence in Charlottesville, Virginia. "He also recently has not demonstrated that he understands the character of this nation. He has not demonstrated that he understands what has made this nation great and what it is today ... and without the things that I just mentioned happening, our nation is going to go through great peril."

Perhaps ominously, Trump's tweet ended with what seemed like a warning: "Tennessee not happy!"