There hasn't been much change to the math underlying that assumption in months. The Republican contest isn't over because Donald Trump clinched a majority before Clinton; he'll do so June 7 as well. It's over because his opponents dropped out, while Sanders hasn't. Trump's hold on his nomination continues to be less secure than Clinton's, but because of the way the Democrats give out delegates, it seems as though the opposite is true.

After last night, Bernie Sanders needs about 66 percent of the remaining pledged Democratic delegates in order to pass Clinton's total. Even though he won most of the delegates last night, he won fewer than he needed to stay on track to pass her. So his magic number — the percentage of delegates he needs to win going forward — once again went up.

This is much harder than it seems. Trump has won nearly every delegate awarded since the contest in Wisconsin, thanks to the Republican rules giving them out in large chunks. The Democratic contest gives them out proportionally, meaning that Sanders needs bigger and bigger wins in bigger and bigger states to catch up to Clinton.

We can game this out. Let's assume that the rest of the states fall about as we might expect: Sanders wins big in the West, the two tie in California, Clinton has bigger wins in New Jersey and the District of Columbia. In that case, if you include superdelegates — a big caveat that we'll come back to — Clinton clinches June 7. (Which is a week before D.C. votes.) She'd end the race leading Sanders by 271 pledged delegates — or by 232 if you include Sanders's superdelegates but not Clinton's.

Now let's assume that the race shifts heavily in Sanders's favor. Let's assume he wins every state until June 7 by 20 points. And he wins California by 10 points, ties in New Jersey, and wins 2-to-1 in every other state that day. Let's say he even ties in D.C., which, given the city's large black population, is all but impossible.

Under that scenario ... Clinton clinches June 7, and closes out the contest with a pledged delegate lead of 163.

It's hard to believe that such a big shift in voting would have such a minor shift in the delegate counts — until you remember that most of the states left to vote have very few delegates (because they have very few voters). Two-thirds of the remaining delegates are in just two states that vote June 7: California and New Jersey.

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What about those superdelegates, you ask? This is the linchpin of any argument that Sanders can win the nomination, that he'll get them to change their minds. It's certainly the case that Clinton has a lopsided advantage among those superdelegates, but even if they were divvied up according to the vote margins in the states they represent, Clinton would have an edge — and would have enough superdelegates for her to clinch the nomination June 7, even under the dramatically pro-Sanders scenario above.

Sanders would need to persuade the superdelegates to back his candidacy disproportionately if he wants the nomination. (It's not clear that Sanders's actual campaign thinks this is an actual viable strategy, mind you.) If he runs the table as in the second scenario, that gets a bit easier, though it requires that the superdelegates essentially ignore the will of Democrats who voted before May and June. It's simply not feasible.