Democratic presidential candidate Bernie Sanders arrives at City Hall Park in Burlington, Vt., on June 13. Sanders took part in a march and vigil for the people killed and wounded during a shooting at an Orlando, Fla., nightclub. (Wilson Ring/AP)

The last ballots of the 2016 Democratic presidential primaries will be cast in Washington, D.C., today. The last ballots to be counted were cast more than a week ago, by Californians who've become the final arbiters of the Clinton-Sanders delegate count — and the focus of some inevitable, conspiracy-minded hand-wringing.

Like the rest of the Pacific coast states, California has moved toward mail-in balloting and built a system that encourages turnout but takes weeks to fully count. On election night, when Hillary Clinton was declared the winner of the state's primary, just 3.5 million ballots had been counted in the Democratic race and just 1.5 million had been counted in the basically uncontested GOP race. But according to Alex Padilla, California's Democratic secretary of state, as many as 8.9 million ballots were cast. Millions of provisional ballots and absentee ballots, which could have been postmarked any time on Election Day, remained outstanding in a race decided by about 440,000 votes.

That's sparked hope among some Sanders supporters that the primary could still be won — a result that wouldn't take away Clinton's delegate majority, but would strike a final blow against a biased media. Sanders himself seemed to encourage the sentiment at his only rally in D.C., telling supporters that "we are standing after having won 22 states, and the results have not yet come in from California."

So far, the molasses-slow count of these ballots has found Sanders improving on his margin from Election Day, while still losing the race. The Associated Press count of votes ended with Clinton at 1,940,580 and Sanders at 1,502,043. Since then, the state has counted 270,561 additional ballots for Clinton and 232,274 for Sanders. That's 53.8 to 46.2 margin for Clinton — tighter than Election Day, tight enough to shrink her overall margin. (And for comparison, just 123,994 people voted in the 2008 D.C. primary for president, a number unlikely to be surpassed today.)

The result has looked a bit like the results in Oregon, where what seemed like a close Sanders win  May 17 turned into a 14-point rout once last-minute ballots were counted. On Election Day, it appeared that Clinton had won California's coastal counties of Santa Barbara and San Luis Obispo. The ballots counted since then flipped both counties to Sanders, and gave him a victory in the 24th congressional district. (Because the district splits its six delegates evenly, that led to no change in the overall count.)

According to the secretary of state, there are 2,303,639 ballots left to process, including 717,862 provisional ballots. More than 500,000 of the outstanding ballots are in Los Angeles County, and more than 150,000 are in Alameda County, a liberal part of the Bay Area where Clinton surprised with an Election Day win. Sanders could improve his vote in both counties, where he campaigned vigorously. But with Clinton's current lead at 476,824 votes, Sanders would need to win 60 percent of the outstanding ballots to pass her — if every outstanding vote was for a Democrat. Since roughly one-third of the late ballots counted so far have been in the Republican primary or for third parties, Sanders would need to win closer to 75 percent of Democratic ballots for a victory, a bigger margin than he won in any primary outside of his native Vermont.

That reality has led to wildly diverging reactions among Sanders supporters. On one catchall Reddit thread, thousands of people have been wondering whether a million ballots ("probably for Bernie") were thrown out. (They were not, although 10 to 15 percent of provisional ballots are often found to be invalid.) Some pro-Sanders media, such as the Justice Gazette, have shared stories about how difficult it was for "no party preference" voters to cast ballots, suggesting that the primary was effectively rigged.

The "rigged" discussion, however, has shifted as the size of the uncounted ballot pile became known. On Wednesday, Sanders supporter and columnist Shaun King tweeted that turnout had plunged in California, perhaps as a result of the Associated Press determining that Clinton had the delegates to win the nomination even before Election Day.

Two days later, King shared a story from Democracy Now, a syndicated radio show with favorable coverage of Sanders, that explained the missing ballot question.

When Sanders meets with Clinton in D.C. tonight, most Democrats will consider the primary over. For plenty of Sanders supporters nervously eyeing the count in California, it won't be.