HARRISBURG, Pa. (AP) — Democrat Joe Biden's narrow but growing margin in the presidential race drew him closer to winning Pennsylvania's cache of 20 electoral votes Friday as county-by-county teams of ballot counters continued to toil.

The canvassing that in a normal year would be wrapping up on Friday will carry into next week, with many counties waiting until Monday to begin going through provisional ballots.

Tens of thousands of remaining mail-in ballots — as well as the provisional ballots and those cast by military and overseas voters — will decide whether Biden's slim lead holds up or if Republican President Donald Trump can find the votes he needs to repeat his 2016 victory in the state.

Starting to count provisional ballots on Monday, some counties decided, will help ensure that they can include all valid mail-in votes arriving by Friday that were sent on or before Election Day. Philadelphia officials said Friday that process may take several days.

In Allegheny County, which includes Pittsburgh, the crew worked through lunch on Friday, counting and sorting ballots. Officials were unsure when their count would be complete.

Allegheny County Executive Rich Fitzgerald had said earlier that counting would continue through the night, but announced at a briefing shortly after 10:30 p.m. that counters were stopping for the night.

“They’ve been doing it with observation, the press is here to watch it, there’s cameras everywhere. So this is a very, very transparent process,” Fitzgerald had said.

Pennsylvania elections officials were not allowed to process mail-in ballots until Election Day under state law, and those ballots have skewed heavily in Biden’s favor after Trump spent months claiming without proof that voting by mail would lead to widespread voter fraud.

There’s another possibility that could delay the results: If there is less than a half-percentage point difference between Biden’s and Trump’s vote totals, state law dictates that a recount must be held.

Under state law, counties must submit unofficial returns to the state on Tuesday and, after a period to allow for recounts, certify their results to the state on Nov. 23.

As people around the world looked on, waiting for results that could sway the presidential contest, some counting locations in Pennsylvania became a magnet for demonstrations and, in some cases, spontaneous festivities.

In Doylestown, a suburb about 30 miles (50 kilometers) north of Philadelphia, a small group of people carrying “count every vote” signs circled the Bucks County courthouse Friday afternoon, banging drums and shaking tambourines while county workers inside continued counting votes.

“We’re also trying to make things more festive than they normally are at these type of events,” said Matt Balitsaris of Tinicum, who carried a drum and wore a black cloak decorated with a large eye.

Pittsburgh lawyer Nicole Nino observed ballot counters inside the Allegheny County elections warehouse for the Republican Party.

“I thought I would come and see how this system is being managed, how ballots are being counted, see if there are discrepancies,” she said, coming away “very impressed with what they’re doing here. It seems to be very methodical, very organized.”

The Trump campaign and the Republican Party argued in court Thursday that GOP election observers were kept too far away from the tabulation in Philadelphia, that some Democratic-leaning counties unfairly allowed people to fix technical problems with their mail-in ballots, and that mail-in ballots arriving after Tuesday should not be counted.

A judge in Harrisburg on Friday dismissed a request from Republicans to keep the state and counties from counting provisional ballots cast by voters whose mail-in ballots had been disqualified by a technicality.

Democratic Gov. Tom Wolf’s state elections bureau last month told counties that voters could use provisional ballots if they “did not successfully vote” with the mail-in or absentee ballot they had been issued, or if their ballot had been rejected and they believed they were still eligible to vote.

The Trump campaign tried to stop the count in Philadelphia itself — alleging city officials were depriving their observers of meaningful access — but a federal judge refused to go along, instead urging the sides to forge an agreement.

Speaking from the White House on Thursday night, Trump made unsupported allegations that Democrats in Pennsylvania and elsewhere were trying to steal the election.

It was unclear whether any of the legal challenges would make a difference to an eventual outcome.

More than 2.6 million mail-in ballots were cast, and there has been no report of fraud or any other problem with the accuracy of the count.

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Associated Press writers Marc Levy in Harrisburg, Michael Rubinkam in northeastern Pennsylvania, Mike Catalini in Doylestown, Juliet Linderman in Pittsburgh and Maryclaire Dale and Claudia Lauer in Philadelphia contributed to this report.

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Find AP’s full election coverage at APNews.com/Election2020.