More than half of the mail-in ballots had been counted as of around 6 a.m., reports say -- and they were heavily in favor of Joe Biden, CBS reports.
If the ballots come out in Biden's favor, that would put in ahead of U.S. President Donald Trump and gain him Pennsylvania's 20 electoral votes.
People rallied across Philadelphia making pushing to have every vote counted.
Gov. Tom Wolf acknowledged the process is slower than usual -- but that means it's working, he said.
"Thousands of local county staff and volunteers are working around the clock to count your vote," Wolf said. "Their work to have a complete and accurate count is not easy, but it's the bedrock of our democracy."
"Let me be clear: Pennsylvania is going to count every vote and make sure your voice is heard. I'm going to fight like hell to protect your vote," Wolf said.
"We'll fight every single attempt to disenfranchise voters, and we'll continue to administer a free and fair election. Every vote counts in Pennsylvania."
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