PITTSBURGH — As Pennsylvania continued to count an estimated 1.4 million outstanding mail-in ballots on Wednesday, Democrats were confident that the results would skew heavily to Joseph R. Biden Jr. and ultimately deliver him a narrow victory over President Trump, whose legal team was descending on the state to mount challenges in court.
Mr. Trump holds a 542,000-vote lead with 78 percent of the estimated total votes reported. Elections offices in the state’s populous, Democratic-leaning cities and suburbs were only partway through tabulating and reporting the bulk of mail ballots.
So far, Mr. Biden has won nearly four in five of the mail votes reported, a reflection of the president’s monthslong disparagement of mail ballots, which led to far fewer Republicans voting by mail than Democrats than Republicans.
If the unreported votes follow the same pattern, said Rich Fitzgerald, the Democratic county executive of Allegheny County, “Joe Biden would probably pick up 1,050,000 voters, Donald Trump would pick up 350,000, for a net gain for Joe Biden of about 700,000 votes.’’
“The distance now is 540,000,” he added. “So Biden probably wins the state by roughly 100,000.’’
Allegheny County, which includes Pittsburgh, expects to report its outstanding mail votes by the end of Wednesday. Other Democratic enclaves, including Philadelphia and its suburban counties, are expected to report in the next one to three days. As of Wednesday morning, more than half of the ballots in Philadelphia had still not been counted.
Looming over the counting, however, are multiple lawsuits filed by Republicans at both the county and statewide level, questioning the process by which voters were notified of issues with mail in ballots and allowed to cast provisional ballots. Hearings are scheduled in both Montgomery County and at the state level on Wednesday.
At a news conference on Wednesday, Gov. Tom Wolf reiterated that election officials would count every ballot remaining.
“Pennsylvania will have a fair election, and that election will be free of outside influences,” Mr. Wolf said. “I will vigorously, and we all will vigorously, defend against any attempt to attack that vote in Pennsylvania.”