Donald Trump speaks during a rally in Eugene, Ore. (AP Photo/Ted S. Warren)

Update: On Thursday morning, the AP announced that, per its calculations, Trump had clinched the nomination. "Trump was put over the top in the Associated Press delegate count by a small number of the party's unbound delegates who told the AP they would support him at the convention," the AP reports.

Somewhat amazingly, Donald Trump has managed to get this close to clinching the Republican nomination before voting on June 7 in California and New Jersey, the two biggest remaining states. It's an outcome that a little over a month ago would have seemed completely impossible, but a string of big wins combined with his remaining competitors leaving the field prompted a tsunami of delegates to fall into place in short order.

Before April 19, the day of the New York primary, Trump needed more than two-thirds of the remaining bound delegates to clinch the nomination before the convention. This was in the wake of Ted Cruz's big win in Wisconsin, and that percentage seemed prohibitive.

Then Trump crushed Cruz and John Kasich in New York, winning every county (save Manhattan) and nearly every congressional district with a majority. The next week, he King-Konged across the rest of the northeastern states, winning 111 of 118 delegates. Finally, in the first contest this month, he won every delegate in Indiana, booting Cruz and Kasich and becoming the presumptive nominee.

Trump won't win every delegate in Washington state, which held its primary Tuesday, thanks to the state's weird rules. (Washington uses proportional allocation of delegates — but relative to every vote cast. Since no one but Trump hit the 20 percent threshold for delegates, Trump's 75-plus percent of the vote (as of writing) will get him 75-plus percent of the 14 statewide delegates — just shy of the total haul.) But he'll win nearly all of them.

Looking only at bound delegates — those who have to vote for him at the convention — Trump needs only about 28 percent of the remaining delegates to clinch the nomination. That's a number that's so low that it's essentially a gimme; he'll probably clinch the nomination with pledged delegates before the sun sets in California in two weeks.

But, again, that's only pledged delegates. That was an important distinction way back in the there-will-be-a-contested-convention days, because Trump couldn't be confident that unpledged delegates would actually vote for him once they got to the convention floor and party elders started twisting their arms and giving them noogies. With the establishment now falling all over itself to make nice with Trump, though, we can feel more confident looping Trump's unbound delegates in the mix. They could change their minds, but they're a lot less likely to than they were a month ago.

The go-to on up-to-the-minnute delegate math is Daniel Nichanian. And here's what Nichanian has to say.

Those two caveats are important ones. The first is that he's using CNN's estimate of Pennsylvania's large pool of unbound delegates, a figure that the Associated Press's numbers put at 40 on Wednesday. Update: It was an increase to this figure, after conversations with unpledged delegates, that prompted the AP to call the race on Thursday.

The bigger part of Nichanian's assumption, though, is the Iowa delegates. As you should have learned by now, each state sets its own rules for how to allocate delegates to the Republican convention. In some cases, the initial delegate counts change after voting is held. In Alaska, for example, delegates are redistributed if a candidate drops out. In Iowa, delegates are bound to candidates unless they aren't actually eligible for the ballot at the convention.

The party has a rule (Rule 40) which states that a candidate must have won a majority of delegates in eight contests to be eligible for the ballot. So far, only Trump and Cruz have hit that mark. If Cruz isn't on the ballot (which is to say, if he is isn't formally nominated) Trump gets all of Iowa's delegates. Per Nichanian's count, that would add 23 delegates to Trump's total — and put him over the 1,237 delegates he needs to clinch.

Responding to a question about a comment he had made earlier in the day, Sen. Ted Cruz (R-Tex.) downplayed expectations that he might consider resuming his presidential campaign while talking to reporters May 10. (Reuters)

But that requires two however-likely theoreticals (unbound delegates staying committed and Cruz not appearing on the ballot). By June 7, it won't matter. Trump will win New Jersey and California, at the least giving him more than enough bound delegates to clinch without any gymnastics. Again, what's remarkable is that we're even talking about how close he is to clinching prior to the last day of voting. Only a few weeks ago, Trump's campaign suggested that he'd win more than 1,400 delegates, a number that at the time seemed hard to believe.

Now it seems inevitable. Once again, Trump has proven the skeptics wrong.

Here's what a Washington Post/ABC News poll conducted May 16-19, 2016 said about the race between Democratic presidential front-runner Hillary Clinton and GOP candidate Donald Trump. (Sarah Parnass/The Washington Post)