Ahead of tonight's televised debate between Sen. John McCain and his Democratic challenger, Congresswoman Ann Kirkpatrick, McCain decided to dump his endorsement of GOP presidential nominee Donald Trump.

In so doing, he has undermined on of Kirkpatrick's best attacks against McCain and eliminated any need to defend the collapsing Trump.

McCain could put up with a lot from Trump: The personal humiliation of having Trump mock his time as a prisoner of war and other tweeted insults; Trump’s repeated praise of Russian overlord Vladimir Putin; the plans to round up all the illegal immigrants in the United States; Trump’s feud with the parents of a fallen serviceman; and Trump’s obvious ignorance of the details of both domestic and international politics.

But after the “grab-them-by-the-pussy” tape emerged last week, McCain finally had a reason to withdraw his endorsement of Trump. In a statement to the press on Saturday, Oct. 8, McCain said that he “wanted to support the candidate our party nominated. 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.

Then he lowered the boom: “But Donald Trump’s behavior this week, 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. Cindy, with her strong background in human rights and respect for women fully agrees with me in this.”

“Cindy and I will not vote for Donald Trump,” McCain concluded. “I have never voted for a Democratic presidential candidate and we will not vote for Hillary Clinton. We will write in the name of some good conservative Republican who is qualified to be president.”

Kirkpatrick, who has built much of her campaign around McCain’s support of Trump, said McCain's decision to dump Trump comes too late.

“John McCain showed today he only cares about one thing: his political career,” Kirkpatrick said in a prepared statement. “His decision is nothing more than a political calculation. It's been more than 24 hours since Trump’s comments were released. If it takes a full day for McCain to decide something is inappropriate, then he clearly doesn't have the leadership Arizonans need. He has abandoned his principles and changed his positions whenever he thought it would help prolong his 33-year career in Washington. For more than a year, McCain stood by Donald Trump, pledging his support more than 60 times. He refused to stand up to Trump when Trump insulted a Gold Star family. He refused to tell Trump to take back his bigoted remarks on immigrants and Latinos. He was silent when Trump mocked a man’s disability. He defended Trump when Trump insulted veterans suffering from post-traumatic stress. McCain made it clear a long time ago: He is no longer a straight-talking maverick. He missed the chance to show political courage and lead. He failed that test.”

McCain has seemed increasingly irritated by the question of whether he still supported Trump after reporters continued to ask him whether the endorsement held following each new outrage. And from what we’ve heard from different sources, McCain has a very deep dislike of Trump, despite his willingness earlier this year to support him.

Given McCain’s weakness among Trump’s most ardent supporters (the folks he called “wacko-birds” when Trump was headed to Phoenix in summer 2015), it’s hardly surprising that he didn’t denounce Trump when he still had a primary challenge on his hands. And even though he easily dispatched former state lawmaker in that primary, McCain insisted he would not be withdrawing his endorsement of Trump in a post-primary pivot. “There’s no reason to do that,” he told Politico in August.

But Pussygate gave McCain—and many other Republicans around the country, such as his pal from New Hampshire, Kelly Ayotte—an excuse to finally disavow Trump. And it came at a time when it could hurt the most: Trump was already tumbling the polls; McCain’s decision to withdraw his support could help Hillary Clinton become the second Democrat—after her husband, Bill Clinton—to win Arizona’s presidential contest since Harry Truman carried the state in 1948.

Still, you have to wonder if McCain would have made the same principled decision if Trump weren’t already circling the drain.