Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeBiden eyeing Cindy McCain for UK ambassador position: report Profiles in cowardice: Trump's Senate enablers McSally concedes Arizona Senate race MORE (R-Ariz.) on Tuesday doubled down on his skepticism of Donald TrumpDonald John TrumpTrump alludes to possible 2024 run in White House remarks Trump threatens to veto defense bill over tech liability shield Tiger King's attorney believes they're close to getting pardon from Trump MORE, saying he currently doesn't believe he'll support the GOP's presumptive presidential nominee in November.

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“As of now, unless he changes significantly, I can’t see myself voting for Donald Trump,” Flake told reporters, according to Bloomberg News, on Tuesday.

The Arizona Republican has been a vocal opponent of Trump, warning that the brash candidate will hurt the Republican Party.

Flake told reporters earlier this year that he would support Ohio Gov. John Kasich over Sen. Ted CruzRafael (Ted) Edward CruzCruz urges Supreme Court to take up Pennsylvania election challenge OVERNIGHT ENERGY: Trump administration proceeds with rollback of bird protections despite objections | Trump banking proposal on fossil fuels sparks backlash from libertarians | EU 2019 greenhouse gas emissions down 24 percent Trump's NATO ambassador pledges 'seamless' transition to Biden administration MORE (R-Texas) or Trump, as the three battled for the party's nomination.

His latest comments come after he told MSNBC's "Morning Joe" on Monday: Trump wasn't "my first nor my 17th choice" to be the party's nominee.

"It's uncomfortable not having endorsed the Republican nominee, I have to say, but I can't at this point," Flake added. "I hope to be able to support the nominee. I certainly can't right now."

Flake had previously endorsed Sen. Marco RubioMarco Antonio RubioPressure builds for coronavirus relief with no clear path to deal The Hill's Morning Report - Presented by Mastercard - Coast-to-coast fears about post-holiday COVID-19 spread Potential 2024 Republicans flock to Georgia amid Senate runoffs MORE (R-Fla.), who ended his bid earlier this year.

Republicans have been distancing themselves from Trump's criticism of Judge Gonzalo Curiel, who is overseeing cases against Trump University. The real estate mogul said Curiel won't be fair because of his Hispanic heritage.

Flake on Monday called Trump's comments "very disturbing."

“His statements this week on the judge, that’s a new level,” Flake said on MSNBC. "It’s not just ill-informed or ignorant statements."