Cameron Joseph contributed reporting.

Sen. Bob Corker (R-TN), who has in recent weeks slammed President Trump as a liar and incompetent leader who is unfit for the White House, told reporters Wednesday that he plans to continue using the Foreign Relations Committee he chairs in the Senate to push back against Trump’s “debasement of our nation” and reign in his executive power.

“We’re going to begin next Monday with the Authorization for Use of Military Force,” Corker said, referring to a bill that would give the military the authority to wage war on extremists around the world—authorization the Trump administration says it does not need.

“We’re going to be looking at the War Powers Act,” Corker continued. “We’ll be very informative to the American people and the rest of the Senate about what powers the President has, shouldn’t have, whatever. It’s going to be a very robust time beginning Monday night.”

Corker announced last month that he will not seek re-election in 2018 to a third term in the Senate. Sen. Jeff Flake (R-AZ), who on Tuesday announced his own retirement in a broadside against Trump and his congressional enablers, also sits on Foreign Relations Committee, putting the two most outspoken voices in the GOP in a position to try to reign in a president they say they no longer trust.

Corker said Wednesday that his committee’s stance will not be radically different than before he and Flake came out swinging, but rather a continuation of their previous independent streak.

“President Trump has never been a factor in how we deal with foreign relations,” he insisted. “For example, Mr. Trump, excuse me, President Trump, was very opposed to the Russia bill that passed 98-2 on the floor.” Corker was referring to new sanctions on Russia passed by Congress over the summer and signed by a reluctant Trump.

Corker said he did not know in advance of Flake’s plan to give a barnburner speech and is not working on convincing any of his other colleagues to buck their party’s president.

“Each senator has to decide how they’re going to comport themselves,” he said. I’m not in any way trying to generate a herd or put pressure on other senators. I never have.”

Amid widespread anxiety that Trump is driving his staunchest critics out of public office, Sen. Susan Collins (R-ME), who has also bucked the President on health care and other issues, told TPM she expects Flake and Corker will use their remaining months in office to speak their minds free of political constraints.

“I don’t think you’re going to see the silencing of Jeff Flake or Bob Corker, and keep in mind that they’re still here until the end of next year and into early January of 2019,” she said.

Unlike Flake and Corker, Collins will be running for reelection when her term is up.

“I have a lot of confidence in the roll Congress plays as a check on the executive,” she said.