Trump critic and Republican Sen. Jeff Flake suggested Sunday that the president’s words and actions have left him open to a primary challenge if he seeks reelection.

“If he continues on the path that he's on, that is going to leave a huge swath of voters looking for someone else,” Flake, who is not seeking reelection in 2018, told ABC News’ “This Week.” He's probably inviting a Republican challenge.”

Flake also said Trump’s continued path could result in a “diminished base” and “a huge swath of voters in the middle that may be looking for something else” -- including a “far left” president like Vermont Sen. Bernie Sanders, an Independent, or Massachusetts Democratic Sen. Elizabeth Warren.

The first-term senator has been perhaps the most outspoken congressional Republican against Trump.

Flake has made clear that he didn’t vote for Trump in 2016. And, he has openly criticized the president on several matters over roughly the past 18 months, including Trump's travel ban affecting mostly Muslim countries -- and more recently the president’s support for Republican Roy Moore, who recently lost the special Senate election in Alabama amid accusations of sexual misconduct decades ago.

Flake, whose opposition to Trump in conservative-leaning Arizona hurt any reelection chances, also said Sunday that Trump “certainly” will face a challenge from an independent candidate, which has happened to every president in recent history.

However, Flake said that he doesn’t plan on seeking the GOP presidential nomination in 2020.

“I don't rule anything out, but it's not in my plans,” he told ABC News.

Flake also suggested he wouldn’t leave the GOP and that Moore’s defeat could turn around the party and help it move away from its "ultra-nationalist" element.

The Associated Press contributed to this report.