HARRISBURG (AP) - Mail-in ballots received by Pennsylvania counties within three days of polls closing will count, the presidential battleground state’s top election official said Thursday, although she cautioned that more litigation could change that.

Late-arriving ballots will be counted separately for the sake of “effective and clear election administration in Pennsylvania,” said Secretary of State Kathy Boockvar

Boockvar had told counties Wednesday to set those ballots aside and not count them. That was hours before the U.S. Supreme Court turned away a Republican Party bid to block a state court order granting the extended deadline for mail-in ballots in Pennsylvania.

“Under the current status of things, they will be counted, but I don’t know, I’m not going to game out what could happen if another filing changes things,” Boockvar, a Democrat, said.

President Donald Trump and former Vice President Joe Biden are hotly contesting Pennsylvania’s 20 electoral votes, as counties prepare to process 3 million mailed ballots, more than 10 times the amount received in 2016’s election.

Any late-arriving ballots could take on enormous importance if Pennsylvania turns out to be the crucial state in the Nov. 3 election and they are potentially decisive. The majority of mail-in ballots are being cast by Democrats, according to state data.

Trump will return to Pennsylvania on Saturday, with rallies tentatively scheduled for Bucks County in suburban Philadelphia, Reading Regional Airport and Pittsburgh-Butler Regional Airport.

With ongoing Republican acrimony over the deadline extension, Boockvar and her boss, Democratic Gov. Tom Wolf, are urging hundreds of thousands of voters who haven’t returned their mail-in ballot to deliver them by hand, instead of trusting the Postal Service to deliver it by Tuesday night.

Wolf said the uncertainty adds to the need for everyone to get their ballots in before polls close at 8 p.m. Tuesday. The Supreme Court, in its decision Wednesday night, did not explicitly say that it is allowable to count late-arriving ballots.

“There’s a lot of noise out there and we don’t know what’s going to happen,” Wolf told a news conference. “The Supreme Court may or may not decide to pick this up again after the election. It looks like this is going to stand at least until the election. But why even have any doubt? It’s in your hands. ... Get it in by 8 o’clock on Election Day.”

That noise on Thursday included Trump tweeting that a “3 day extension for Pennsylvania is a disaster for our Nation, and for Pennsylvania itself. The Democrats are trying to steal this Election. We have to get out and VOTE in even larger numbers. The Great Red Wave is coming!!!”

Democrats say Trump is mounting a massive voter suppression and voter intimidation campaign to keep people from voting in Pennsylvania.

In September, the state Supreme Court, citing concerns over Postal Service delays and massive number of people voting by mail to avoid contracting the coronavirus, ordered a three-day extension past Election Day for counties to receive and count mail-in ballots.

Most states make Election Day the deadline for regular mail-in or absentee ballots, but more than 20 states have a post-Election Day deadline.

Meanwhile, a growing number of counties - at least five, including Cumberland, Monroe and Beaver - are planning to begin the laborious task of processing or counting mail-in ballots starting Wednesday, the day after the election.

Wolf and his fellow Democrats in the state Legislature had pressed for legislation allowing counties to process mail-in ballots before Election Day so that those ballots could be counted on election night, but Republicans blocked it.

As a result, election night returns in many counties are unlikely to account for some or all mail-in ballots, even in counties that begin processing them on Election Day.