Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeThe unflappable Liz Cheney: Why Trump Republicans have struggled to crush her  Cindy McCain: Arizona election audit is 'ludicrous' The Republicans' deep dive into nativism MORE (R-Ariz.) on Tuesday doubled down on his skepticism of Donald TrumpDonald TrumpCaitlyn Jenner on Hannity touts Trump: 'He was a disruptor' Ivanka Trump doubles down on vaccine push with post celebrating second shot Conservative Club for Growth PAC comes out against Stefanik to replace Cheney 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 CruzThe unflappable Liz Cheney: Why Trump Republicans have struggled to crush her  The Memo: The GOP's war is already over — Trump won Hawley says Cheney 'spiraling,' 'out-of-step' amid Trump backlash 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 RubioThe unflappable Liz Cheney: Why Trump Republicans have struggled to crush her  Crist launches bid for Florida governor, seeking to recapture his old job The Hill's 12:30 Report - Presented by ExxonMobil - Trump, Cheney trade jabs 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."