Many Bernie Sanders supporters are holding out hope that by the time California finishes counting its 2016 Democratic presidential Primary ballots, he might emerge with a victory, a photo finish or something closer than the double-digit loss to Hillary Clinton announced by the Associated Press a week ago on election night.

That’s because out of 9.2 million ballots cast across California, 2.3 million remain unprocessed, according to the Secretary of State’s tally as of 5pm Monday. As 58 county registrars and their staffs keep counting ballots across California, the balance in at least three counties has shifted from an election night call for Clinton to emerging slight leads for Sanders. Santa Barbara, located on the central coast, is the highest-profile example.

While many hardcore Sanders supporters—such as National Nurses United executive director Rose Ann Demoro—are not giving up, there are reasons why the vote count is taking several weeks to complete, just as the slight shift in results in Sanders’ direction does not look to be sizable enough to change the primary’s outcome.

“There’s maybe been a 1 percent gain for Sanders between election night and now,” said Alameda County Registrar of Voters Tim Dupuis.

The Bay Area county where Oakland is located is a good illustration of these two dynamics: the slow count and the slight but insufficient shift toward Sanders.

Let’s start with the unprocessed ballots. The short explanation is millions of Californians vote by mail and in person at polling places, and the counties have to verify all the paper ballots to make sure they are legal and people aren’t voting more than once. With millions of people voting, that takes time.

California’s counties process ballots in waves, by category: those that arrive before election day; those cast on election day (including provisional ballots given to people whose names were not on polling place lists); and those that arrive in the mail afterward. Thus, in the days that followed last Tuesday’s primary, the total number of ballots processed—out of 9.2 million cast statewide—has been steadily increasing, even though 2.3 million remain unprocessed.

Alameda County is typical. At 2am the morning after Tuesday’s election night, it reported 91,324 votes for Sanders and 107,102 votes for Clinton, Dupuis said. That’s a 46 percent to 54 percent split. By last Friday, the county had processed 101,218 votes for Sanders and 118,035 for Clinton, yielding the same percentages. Democrats allocate national convention delegates proportionally, so the county’s primary results remained the same. This county, where Sanders had one of his biggest Northern California rallies, has the fourth largest number of unprocessed ballots in the state, according to the California Secretary of State’s website update at 5pm on Monday. Those 151,853 unprocessed ballots were from people who voted by mail (109,853) and so-called provisional ballots (42,000), which were issued to people whose names were not on polling place voter lists.

Dupuis said his staff has to go through each of those ballots to verify the eligibility and the signature, ensuring that it matches the registration form, or if the person registered online, their driver’s license. This is done in stages. The first mail-in ballots to be counted are those that arrive before election day. Those are processed and included with polling place vote results on election night, which, in his county’s case, were published the next morning at 2am.

Then, there is another wave of unprocessed mail-in ballots to count, he said, those dropped off at polling places on election day or that are received in the mail up to three days after June 7’s primary. Those have to be checked against polling place precinct lists, he said, to ensure that nobody voted twice. Then they go through the same signature verification process and the voter’s selections are recorded and added into the county totals.

“We are an all-paper election system—that is throughout all of California,” Dupuis said. “We use some automation to help with the tally. But we can always go back to the paper source.”

The Secretary of State’s press office explained that the counties have one month to process and certify the primary results. In that time period, they don’t have to report daily to the state, even though some do. That means it will be several weeks before the final presidential results are known. But it’s possible to contact county election offices to get updates.

Dupuis, reached midday Tuesday, said his office finished counting all of Alameda County’s mail-in ballots on Monday—the 109,853 described as unprocessed by the Secretary of State’s webpage. As of 5pm Monday, the tally was 134,509 votes for Sanders, or 46.66 percent, and 151,189 votes for Clinton, or 52.45 percent, Dupuis said, pointing to the county’s website.

That leaves Alameda County with 42,000 provisional ballots to process, he said. But even then the official counting will not be over, as the state requires 1 percent of a county’s ballots to be handcounted, as an audit for accuracy, before the presidential primary results are certified. That’s what’s taking so long, especially in Los Angeles, the nation’s largest election district.

Election integrity activists, many of whom are Sanders supporters, should be pleased that the largest state is using a verifiable paper ballot trail, even if it takes weeks to get final results. But this laborious process is not taking place in front of the public—or regional media—which leads some people to speculate that something nefarious is afoot. (Other states using all-electronic voting systems can’t audit or recount their votes at all, in contrast.)

Nonetheless, the small gains made by Sanders against Clinton as the California vote count process keeps going forward are unlikely to be of the magnitude needed to change 2016’s Democratic presidential nominating results. Sanders, who California pre-election polls reported was trailing Clinton by 2 percent, needed to win two-thirds of the state’s delegates to come close to matching her in pledged Democratic National Convention delegates.

The early and ongoing returns—seen on this statewide map from the California Secretary of State—showed Clinton winning across almost all of populous Southern California and Sanders winning in the northern and mountainous regions. The counties with the most unprocessed ballots were Los Angeles, San Diego, Sacramento and Alameda.

That’s why taking a closer look at the vote count in Alameda County is instructive, because if Sanders is not making sizable late-breaking inroads in that urban epicenter, he’s unlikely to gain more ground elsewhere.

The 2016 Democratic primary and caucus process ends Tuesday in Washington, D.C. Sanders has said he will address his supporters after the primary about his future plans. But it’s unlikely that the final numbers in California’s primary will change the contest’s dynamic or his presence at the Democratic National Convention in Philadelphia in July.