This is the week that the Republican Party’s worst nightmare came true: Donald Trump emerged as the presumptive presidential nominee after crushing the competition in Indiana’s GOP primary.

The party didn’t handle it so well.

House Speaker Paul D. Ryan kicked it all off, telling CNN’s Jake Tapper that he simply can’t support Trump yet. “I’m just not ready to do that at this point,” Ryan said. “I’m not there right now. And I hope to, though, and I want to.”

The hits just kept coming.

South Carolina Sen. Lindsey Graham, a one-time presidential candidate, quickly made clear that his criticism of Trump wouldn’t end now that the real estate mogul was the party’s only remaining choice. “I also cannot in good conscience support Donald Trump because I do not believe he is a reliable Republican conservative,” Graham said as a part of an extended tweetstorm explaining why he wouldn’t be voting for his party’s nominee or attending the national convention in July.

Graham’s announcement was quickly followed by a similar one from former Florida Gov. Jeb Bush. In a Facebook post, Bush lambasted Trump as someone ” who has not demonstrated that temperament or strength of character. He has not displayed a respect for the Constitution. And, he is not a consistent conservative. These are all reasons why I cannot support his candidacy.”

Trump was positively Trumpian in his response to all the angst he has created within the party he will represent this fall. A Trump spokeswoman suggested that it might be time for someone other than Ryan to be speaker. And Trump unleashed this doozy on Graham: “Every time I see Lindsey Graham spew hate during interviews, I ask why the media never questions how I single-handedly destroyed his hapless run for president.”

What’s next is anybody’s guess. The party appears to be teetering on the edge of a full-blown split between those who believe that now that the voters have spoken it’s time to get behind Trump and those who view backing the billionaire as an abandonment of the true principles of conservatism.

And there’s no one able stop it. Republican National Committee Chairman Reince Priebus has the most difficult job in America. Trump lacks the unity gene. Lots of other eminences grises within the party — the Bushes, Bob Dole, and so on and so forth — are on opposite sides of the divide and seem to have no interest in serving as a bridge.

That means it’s likely that the schism will get worse before it gets better. If it gets better. A party being torn in two is bad enough. That process happening within 184 days until a presidential election and in full view of the general public is even worse. And this might not even be the bottom yet.

(c) 2016, The Washington Post · Chris Cillizza