Bernie Sanders greets people after speaking at a rally at the Big League Dreams Sports Park on Wednesday May 25, 2016 in Cathedral City, CA. The primary in California is June 7th. (Matt McClain/ The Washington Post)

Bernie Sanders's efforts to stay in the ring with Hillary Clinton have been aided by a decision made by outside actors a long time ago. The last state from which we will get primary results on the Democratic side is a big, liberal one: California. For all of Sanders's consistent arguments about momentum -- first in the run-up to the New York primary, then from Indiana to California (with the annoying speed bump of Kentucky) -- it's always been California that would be his campaign's last, best argument for owning the hearts and souls of the Democratic Party as the convention loomed.

A new poll from the Public Policy Institute of California offers Sanders some good news. After trailing Hillary Clinton by 7 points in PPIC's March poll, he now trails by 2 -- what observers would call a virtual dead heat. There was some odd movement among demographic groups between the two surveys, including that Sanders went from leading with white voters by 5 points to trailing by 6. But the poll helps bolster Sanders's argument that he may win the state, though the Real Clear Politics average (thanks in large part to a dearth of recent polls) still shows Clinton with a big advantage.

In her report from Sanders's campaign efforts in the state, The Atlantic's Molly Ball quotes the Vermont senator's closing argument. "I believe that if we win here in California," he said at a rally in Santa Monica, "and if we win the other five states that are voting on June 7, we’re going to go marching to the Democratic convention with a hell of a lot of momentum. I believe that if we do well here in California, we'll march in with momentum and we’ll march out with the Democratic nomination!"

There's just one, big wrinkle in that plan -- setting aside the fact that state wins are meaningless and that Sanders will almost certainly lose one of those five states, New Jersey. California will be the last state to report results, but it's not the last contest. The last contest is in D.C. on June 14, where the electorate will be largely black. And in 2016 Democratic contests for which we have exit polling, Clinton's averaging a nearly 4-to-1 margin of victory among black voters.

Sanders has repeatedly diminished the results of contests in places with large black populations. In the past, he dismissed Clinton's early delegate lead to the fact that states "in the most conservative part of the country" -- that is, the South -- got to vote before other places. (That Sanders won deep-red states like Nebraska, Oklahoma, Wyoming and Idaho is usually not mentioned.) The percentage of black voters has been a strong predictor of the outcome of Democratic contests, so to argue that he has the will of the party, Sanders must almost necessarily pretend that contests he loses in heavily black areas didn't happen.

But that will become tricky in a few weeks. Whatever happens in the elections on June 7, the last contest on the Democratic side will almost definitely be won in resounding fashion by Hillary Clinton.

In a video posted by his campaign, Democratic presidential candidate Bernie Sanders appeals to California voters ahead of the state's June 7 primary. (Bernie Sanders)

It's easy to dismiss that contest, as you might dismiss, say, Guam. It's just D.C., not even a state. Well, included in Sanders's five-state-momentum argument are the great states of North Dakota and Montana. In the 2008 primaries, almost 64,000 Democrats came out to vote in D.C., compared to 28,000 in Montana. And North Dakota in total is only slightly larger than D.C., with a base of Democratic voters that's almost certainly smaller. (North Dakota doesn't require voter registration, so it's hard to compare.)

So over the last six contests, Clinton will win two, New Jersey and D.C. -- the second- and fourth-largest in the lot. Sanders will win North Dakota and Montana, the two smallest. California and New Mexico could probably go either way.

That's not a strong case for momentum.

All of this sets aside the fact that the delegate math for Sanders is beyond prohibitive. Among the other results on June 7 will be the most important one: Clinton will almost certainly clinch the nomination, thanks to her big advantages in pledged and superdelegates. Perhaps that Sanders fan's song will sway a superdelegate or two to ditch Clinton, but it seems unlikely.

It's really not clear what it would take at this point for superdelegates to bail on Clinton, since no matter what has happened, they haven't. Without the superdelegates in the picture, the race would essentially be over, since Sanders wouldn't have that wild card to offer in his defense, and he can't catch Clinton's pledged delegate lead without winning California by a massive margin.

The PPIC poll suggests that the California results may be much closer than we might have assumed a few months ago. But what the state offers isn't a path for Sanders to clinch the nomination. What it offers is the feather in Sanders's cap after a remarkably well-fought primary, in which he's already won most of the policy battles he set out to win.