Sen. Bob Corker (R-TN) admitted on Tuesday night that he has not ruled out primarying President Donald Trump for the Republican presidential primary in 2020.

When asked by reporters on Tuesday if he plans to run for president in 2020, Corker said, “I have not ruled it out.”

Reporters noted that media figures often ask Sen. Corker this question, to which the retiring Tennessee Republican usually answers in a vague manner.

this is my favorite oft-repeated question in the Senate basement, to which Bob Corker always offers a similarly vague answer https://t.co/4ptmylFNYo — Haley Byrd (@byrdinator) November 13, 2018

Corker announced his retirement in September 2017 amidst increasing unpopularity in his home state, which arose from his frequent criticism of the president and his America First agenda.

He received criticism for praising Democrat and former Tennessee Gov. Phil Bredesen during the Tennesse Senate election to replace him, in which he admitted that he has closer ties to Bredesen compared to Rep. Marsha Blackburn who will replace Corker as one of Tennesee’s U.S. senators in January.

Corker also said on Thursday that he would back legislation to protect Special Counsel Robert Mueller if it came to the Senate floor for a vote. The legislation arose as Trump appointed Matt Whitaker to serve as his Acting Attorney General.

Corker said, “I think Mueller needs to be protected, and if something like [the Mueller protection bill] were to come to the floor, I can’t imagine not voting for it.”

Republican Sen. Bob Corker: "I think Mueller needs to be protected, and if something like [the Mueller protection bill] were to come to the floor, I can't imagine not voting for it." — Tim Mak (@timkmak) November 13, 2018

Corker joins fellow Never Trump Sen. Jeff Flake (R-AZ), who said last week that “somebody needs to run” against Trump for the 2020 Republican presidential primary nomination.

Flake floated the name of Ohio Gov. John Kasich and Sen. Ben Sasse (R-NE) as potential challengers to President Trump.

Meanwhile, Flake told CNN in November that he preferred former President Barack Obama’s “tone” on immigration over President Trump’s.

I certainly don’t like the tone that President Trump has taken with regard to blaming immigrants. Having that ad, which I thought was just sickening,” Flake explained. “And frankly, very untrue with regard to the threat that is posed by illegal immigrants.”

President Trump excoriated both Corker and Trump over his time in the White House, explaining that they both had to retire due to their record unpopularity.

“The reason Flake and Corker dropped out of the Senate race is very simple, they had zero chance of being elected,” Trump wrote in October 2017. “Now act so hurt & wounded!”