WASHINGTON — “What does this say about your party that this is your standard bearer?”

The headlines from President Obama’s excoriation of Donald Trump on Tuesday rightly highlighted his flat declaration that the Republican nominee is “unfit to serve as president.” But the challenge to Republican leaders who fell in line behind Trump was even more devastating.

Obama was not simply condemning a man whose brutal cruelty finally came home to anyone with a heart after Trump’s attacks on a Gold Star family. The president was also indicting the entire GOP leadership for courting the extremism that led to Trump and for acquiescing in his nomination.

Let’s focus on the most revealing aspect of this week’s turmoil within a party now aghast over the unstable egotist at the top of its ticket.

Trump could falsely claim that Obama was born abroad, but that wasn’t enough to disqualify him. He could call Mexican immigrants “rapists,” but that wasn’t enough to disqualify him. He could lie repeatedly — about, for example, whether or not he had met Vladimir Putin and whether he had opposed the Iraq War — but that wasn’t enough to disqualify him. He could call for a ban on Muslim immigration to the United States, but that wasn’t enough to disqualify him. He could make degrading comments about women and mock people with disabilities, but that wasn’t enough to disqualify him.

No, it seems, all this and more were sufficiently within the bounds of acceptability for House Speaker Paul Ryan to tell delegates to the Republican National Convention that “only with Donald Trump and Mike Pence do we have a chance at a better way.”

So what really set off the crisis in the Republican Party this week? Trump suddenly became unacceptable because, in an interview with Philip Rucker of The Washington Post, he refused to endorse Ryan and John McCain in their Republican primaries.

No matter what Trump said, Reince Priebus, the Republican national chairman, was willing to bow and scrape before Trump for months in trying to pull the party together behind him. Now, and only now, is Priebus reported to be “furious” and “apoplectic” at Trump. The message: Trump can say anything he wants about women, the disabled, Mexicans and Muslims, but how dare The Donald cause any trouble for Priebus’ friend Paul Ryan?

The corruption of a once great political party is now complete.

The sense of emergency is so profound that there is now talk of how the Republican National Committee might replace Trump as the nominee. Given how discombobulated and degraded GOP politics has become, anything is possible — though it’s a little late. There was active, organized resistance to Trump before the Cleveland convention. But Priebus, Ryan and Senate Majority Leader Mitch McConnell put down the Never Trump insurgency. And their reasons for doing so are instructive.

Let’s go back to Ryan. At the convention, he declared that the year could “end in the finest possible way — when America elects a conservative governing majority.” Translation: Forget how bad Trump is; he’s the guy who’d sign our bills to cut taxes, shred regulation and repeal Obamacare. On “Meet the Press” in June, Ryan explained that Hillary Clinton would not “agree with any of the conservative reforms we’re trying to do.”

But Trump was A-OK on ideology. “I have spoken with our nominee a number of times about our agenda, about conservative principles, and about the policies we need to put in place in order to save the country,” Ryan said confidently. “And we have so much more common ground than any other thing. And that is why I’m voting for our nominee.”

Ryan — unlike Republicans such as Meg Whitman and Rep. Richard Hanna of New York, both of whom endorsed Clinton on Tuesday — will have to live with those words, whatever happens to Trump.

Of course, all of us have our philosophical leanings, and I freely acknowledge that mine are different from Ryan’s. But many other conservatives and many other Republicans saw early on that Trump would be the least appropriate nominee in their party’s history: a walking moral disaster, a ticking psychological time bomb, a torrent of prejudices, and a man of bottomless vindictiveness. They refused to submit to the intolerable and were willing to accept four years of Clinton to save their party.

But most of the GOP’s leaders thought they could domesticate Trump and use him for their ideological purposes. They are now confronting the consequences of being so profoundly wrong.

E.J. Dionne is a columnist with The Washington Post. His email address is: ejdionne@washpost.com. Twitter: @EJDionne.