WASHINGTON ― Sen. John McCain (R-Ariz.), a former Republican presidential nominee who stood by Donald Trump even after he personally attacked him for being a prisoner of war, officially revoked his endorsement of Trump’s presidential campaign on Saturday.

“I have wanted to support the candidate our party nominated,” McCain said in a 251-word statement. “He was not my choice, but as a past nominee, I thought it important I respect the fact that Donald Trump won a majority of the delegates by the rules our party set. I thought I owed his supporters that deference.”

“But Donald Trump’s behavior this week,” McCain continued, “concluding with the disclosure of his demeaning comments about women and his boasts about sexual assaults, make it impossible to continue to offer even conditional support for his candidacy.”

McCain said he ― and his wife ― would write in the name of some “good conservative Republican who is qualified to be President.”

McCain’s decision is a dramatic signal to the party, as GOP voters weigh whether they can support Trump after hearing him speak about groping women in vulgar, boorish terms.

The GOP is rapidly disowning its nominee, with many lawmakers telling their constituents that they won’t vote for Trump and some even calling on him to step aside. You would now have to go back 20 years to find a former GOP presidential nominee who supports Trump ― and, at this rate, news of 1996 Republican nominee Bob Dole pulling his endorsement could come at any minute.

McCain’s withdrawal of support is also notable for the long string of offenses that he has tolerated, including Trump ridiculing the senator in July 2015 by telling a crowd in Iowa that, “I like people who weren’t captured.”

No woman should ever be victimized by this kind of inappropriate behavior. He alone bears the burden of his conduct and alone should suffer the consequences. Sen. John McCain

McCain has shown uneasiness with Trump as the nominee since then. But he has stuck with him, citing his desire to support the party’s chosen standard-bearer. In his statement, McCain names some of the more egregious offenses Trump has made throughout this election.

“In addition to my well known differences with Donald Trump on public policy issues, I have raised questions about his character after his comments on Prisoners of War, the Khan Gold Star family, Judge Curiel and earlier inappropriate comments about women,” McCain said. “Just this week, he made outrageous statements about the innocent men in the Central Park Five case.”

McCain goes on to note that there no excuses for Trump’s “offensive and demeaning” comments.

“No woman should ever be victimized by this kind of inappropriate behavior. He alone bears the burden of his conduct and alone should suffer the consequences,” McCain said.

McCain is up for re-election this November himself, but he appears to have a good handle on the race. HuffPost Pollster shows him with a 10-point lead over his Democratic challenger, Rep. Ann Kirkpatrick.

Of course, Trump’s comments could potentially shake up every race on the ballot ― including McCain’s. He, too, will have to answer for supporting Trump up to this point. Kirkpatrick seized on the announcement, saying McCain’s “decision is nothing more than a political calculation.” Democratic Senatorial Campaign Committee Director Tom Lopach called it “too little, too late.”

But the unendorsement, at least outwardly, appears to be the move of someone less concerned with the immediate politics and more someone who simply couldn’t take Trump anymore.

This story has been updated with statements from Ann Kirkpatrick and Tom Lopach.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.