The two parties held dueling news conferences in Philadelphia early in the day, with Mr. Trump’s supporters insisting his lead would hold statewide and the city’s Democrats, led by former Representative Robert A. Brady, unveiling an analysis of the remaining vote count that concluded Mr. Biden would win Pennsylvania convincingly.
In Georgia, the counting of ballots in numerous counties continued to erode Mr. Trump’s advantage in the traditionally Republican state: By Thursday night, he was leading by about 1,800 votes out of nearly five million cast.
Tens of thousands of ballots remained to be counted in the state late in the day, including many in Chatham County, a Democratic-leaning county along the Georgia coast that is home to Savannah, and many thousands more from Atlanta-area counties that also lean Democratic.
Georgia’s Republican Party has said it plans to bring up to a dozen lawsuits in the state.
In Arizona, Mr. Biden’s lead was down to about 46,000 votes, significantly less than it was on election night. There are over two hundred thousand ballots left to count, with many coming from Phoenix’s Maricopa County.
Officials in Maricopa said they would post another report on Friday morning.
“We’re plugging along and making it happen,” said Adrian Fontes, the Democrat who oversees elections in the county.
The vote count in Maricopa has grown tense, however, since several armed protesters showed up at the county office Wednesday night. On Thursday afternoon, about 200 supporters of Mr. Trump also gathered in front of the headquarters of the Arizona Republican Party after a protest earlier in the day involving about 50 Trump supporters dissipated in front of City Hall in Phoenix.
Some in the crowd held signs reading “Don’t Steal Elections,” “Shame on Fox News” and “Recall Fontes.” (Fox News called Arizona for Mr. Biden on Tuesday night, inflaming Trump supporters.)