Retiring Arizona Republican Sen. Jeff Flake — who is one of President Trump’s most strident Senate critics — refused Sunday to rule out a 2020 presidential bid. He made his remarks Sunday during an interview on ABC News’ “This Week.”

“I don’t rule anything out, but it’s not in my plans,” Flake told ABC News’ Jonathan Karl. “That’s not in my plans. But I do wonder, I do worry that in the future we’ll be faced with a President Trump running for re-election on the one side, drilling down hard on a diminishing base. And on the other side, you might have somebody like Bernie Sanders, or Elizabeth Warren on the far Left of the Democratic Party.”

That, said Flake, “leaves a huge swath of voters in the middle that may be looking for something else.” Flake’s comments to Karl were the first mention anywhere of the Arizonan as a possible 2020 presidential contender.

Flake, who refused to vote for Trump in 2016, denounced the chief executive on October 24 while announcing he would not seek re-election in 2018 amid dwindling popularity in his own state.

[lz_ndn video=33375746]

Karl pressed Flake, asking if he would be “more likely to run for the Republican nomination against the president or as an independent candidate.”

“Like I said, I haven’t thought that deeply about it,” Flake deflected. “But I do believe if the president is running for re-election, if he continues on the path that he’s on, that is going to leave a huge swath of voters looking for someone else.”

Although he declined to say whether he would challenge Trump for the GOP nomination, Flake emphasized Trump is “probably inviting a Republican challenge” and “an independent challenge.”

Related: Sen. Jeff Flake Drops Out

The Arizona senator also took a swipe at Trump’s populist conservative agenda, which champions “America First” policies when he warned the GOP “most definitely” would lose the House and the Senate if the party fully embraced “the Trump direction.”

Who do you think would win the Presidency?

By completing the poll, you agree to receive emails from LifeZette, occasional offers from our partners and that you've read and agree to our privacy policy and legal statement.

Flake apparently feels disgust toward Trump’s core of supporters, telling Karl that “when you look at some of the audiences cheering for Republicans sometimes, you look out there and you say, ‘Those are the spasms of a dying party,’ when you look at the lack of diversity sometimes.” He added that “anger and resentment are not a governing philosophy.”

A Morning Consult poll published in late October showed Flake was the second most-unpopular senator in the country, with a 48 percent disapproval rating among his home state constituents. A survey from the left-leaning Public Policy Polling in August showed just 18 percent of voters approved of Flake’s job performance.

PoliZette writer Kathryn Blackhurst can be reached at [email protected]. Follow her on Twitter here.