Rep. Justin Amash (Mich.), a vocal critic of President Trump who left the GOP last week, said Sunday he's not ruling out a presidential run.

Amash told Jake Tapper on CNN's "State of the Union" he would consider running as an independent.

"I still wouldn't rule anything like that out. I believe that I have to use my skills, my public influence, where it serves the country best. And I believe I have to defend the Constitution in whichever way works best," he said.

Amash announced in a Washington Post op-ed Thursday that he was leaving the Republican Party.

He had been the only member of the GOP to call for impeachment proceedings against President Trump.

In his op-ed, Amash did not specifically call out Trump.

He told CNN on Sunday that he has had concerns with the Republican Party for several years and that "this term in Congress has really shown how bad it can get."

Amash said he plans to run for reelection to his congressional seat and is "very confident" he will win despite leaving the party.

He faces a Republican challenger, Jim Lowe.