PHOENIX — Joseph R. Biden Jr. held onto a narrow lead in Arizona after elections officials added thousands more votes to the results there on Saturday morning in what is likely to be one of the last large reports of new vote data from the state.
Just before 11 a.m. on Saturday, roughly 6,800 more votes were added to the statewide tally, shrinking Mr. Biden’s lead slightly to about 28,000 votes. Then, about 10 minutes later, the tally of more than 45,000 additional votes was reported by Maricopa County, the largest county in the state, winnowing Mr. Biden’s lead further to about 20,000 votes. Officials in Maricopa County, which includes Phoenix, said the Saturday afternoon data dump would be the last large report of tallied votes they planned to release.
Although ballots counted on Friday and Saturday have tilted in Mr. Trump’s favor, Mr. Biden was firmly ahead of the president in Maricopa County after the latest batch of votes were tallied. If the results hold, 2020 will be the first time that Maricopa County voters have chose a Democrat for president in more than 70 years.
The scene was calm on Saturday morning at the tabulation site near downtown Phoenix where Maricopa County employees were continuing their work. Only two protesters were standing in the parking lot where protests, some involving armed supporters of Mr. Trump, had unfolded this week.
One of the men in the parking lot held an American flag and said he was at the site as a single-issue voter, explaining that he was an anti-abortion campaigner. He declined to give his name.
The other pro-Trump protester was Franklyn Olivieri, 50, a Brooklyn-born construction worker who has lived in Arizona for more than two decades.
“We just want a fair count,” Mr. Olivieri said. “If it needs to go to the courts, go to the courts.”
Both of the men said they hoped any demonstration on Saturday would be peaceful.
Even Mr. Biden’s narrow edge in Arizona after days of ballot counting underscored a profound political shift in the state, a longtime Republican bastion that has lurched left in recent years, fueled by rapidly evolving demographics and a growing contingent of young Latino voters who favor liberal policies.
In one of the brightest spots for Democrats so far, the former astronaut Mark Kelly defeated the state’s Republican senator, Martha McSally, in a special election, making Mr. Kelly and Kyrsten Sinema the first two Democrats to represent Arizona in the Senate since the 1950s.