GOP Sen. Jeff Flake isn’t ruling out a primary challenge to President Trump in 2020.

“I won’t go there. That’s a long time away,” the Arizona senator told CNN, when asked if he or another Republican should oppose Trump in the next election. “It’s early. Time will take care of itself.”

Flake announced that he would not be seeking re-election on Tuesday in an emotional speech that sharply criticized Trump and his leadership.

After the speech, he told CNN that Republicans like himself, who are willing to criticize the president, have a “narrow path” to election.

“I would have to run a campaign that I couldn’t be proud of,” he said. “And I chose not do that.”

Flake, who said he believes the president is setting a bad example for children, called out Trump for tweeting at foreign leaders and referring to Democrats as “losers or clowns.”

“These are kinds of things that we shouldn’t be okay with,” he said. “We keep waiting for a pivot that simply isn’t happening.”

On Tuesday, GOP Senator Bob Corker of Tennessee also criticized Trump, standing by his comments that the White House is an “adult day care center.” The president later tweeted that Corker “couldn’t get elected dog catcher in Tennessee.”

When asked if he was forming a ticket with Flake in the 2020 primary, Corker said yes, in “the dogcatcher field … I do like dogs,” according to the Associated Press.