We can no longer pretend this isn’t happening. Donald Trump will very likely be the Republican nominee for president, and there is a nonzero chance he could win in November.

Trump won at least four of the primary contests Tuesday, including winner-take-all Florida. If you count Missouri, where he seems to have beaten Ted Cruz by a scant 1,726 votes, he won five out of six, losing only in John Kasich’s home state of Ohio. Cruz and Kasich are his only remaining rivals — all others have been vanquished — and Trump has won more primaries and convention delegates than the two of them put together.

If we were talking about a normal candidate, rather than a dangerous demagogue, we’d say he had pretty much sealed the deal for the nomination. But otherwise sensible people seem to be gambling on some kind of miracle — rather than focusing on what needs to be done to keep Trump out of the White House.

The stop-Trump “movement” in the Republican Party has been, thus far, a pathetic joke. The fecklessness of the whole endeavor was encapsulated by Mitt Romney’s performance earlier this month: He told voters why they should not vote for Trump, but stopped short of endorsing an alternative.

The party establishment has no hope of defeating Trump if it is not willing to coalesce around one of his opponents. I understand that Cruz — the logical choice, since he has actually beaten Trump multiple times in primaries and caucuses — is widely disliked and almost certainly too conservative to win the general election. I understand that Kasich is seen as too moderate and has not demonstrated much appeal to the base. But if party leaders can’t bring themselves to choose one or the other, Trump will continue to roll.

Big-money GOP donors seem stunned into paralysis. Many of them supported either Jeb Bush, who bowed out last month after a drubbing in South Carolina, or his fellow Floridian, Marco Rubio, who withdrew Tuesday after being routed in his home state. No politician is invulnerable; a massive, sustained, well-financed media campaign against Trump in the states yet to vote could hurt him. But no one seems willing to coordinate or fund such an effort, and time is fast running out.

Given Trump’s performance Tuesday, it looks increasingly possible that he will arrive at the convention in Cleveland with the 1,237 delegates needed to win the nomination. But it will be close, and he may end up with just a strong plurality, not a majority. This opens the possibility of a contested convention, which could, after several ballots, give the nod to someone else.

In typical strongman fashion, Trump ventured that “I think you’d have riots” if the party did such a thing. Given the tension that surrounds his rallies, he may be right. But I have a hard time believing the GOP establishment would even attempt such a maneuver, let alone bring it off.

Snatching the nomination from a candidate who has demonstrated such popular appeal with the party base would be an act of self-sacrifice by the establishment. It might be the right thing for the nation as a whole, but it would fracture the GOP and all but ensure defeat in November.

There are signs that some leading party figures are becoming resigned to the prospect of Trump as their candidate. Uber-strategist Karl Rove, who has been a loud and steady anti-Trump voice, had a column in The Wall Street Journal on Wednesday in which he offered Trump “ten bits of unsolicited advice” to help “raise your game.” The first suggestion was laughable: “Change your tone.” Where Trump is concerned, that’s the same as saying: “Become a different person.”

In his primary-night appearances at Mar-a-Lago, his Florida estate, Trump has begun calling for party unity. He may get it, or at least an approximation. Some establishment Republicans will decide it’s better to let Trump suffer a crushing loss and rebuild the party afterward, rather than tear it apart at the convention.

That would be an abdication of responsibility. Great political parties do not nominate for president someone who so glaringly lacks the knowledge and temperament to be the leader of the free world. But here we are.

In a general election, probably against Hillary Clinton, Trump almost surely loses. But there is always some degree of risk. Everyone should realize that “Clinton fatigue” is no excuse for electing a man such as Trump to the highest office in the land.

Eugene Robinson’s email address is eugenerobinson@washpost.com.