That battleground state, with the largest trove of electoral votes still up for grabs, had hundreds of thousands of outstanding mail-in ballots to count as Mr. Trump’s lead narrowed to about 136,000 votes Thursday morning.
Georgia is critical to the balance of power in the Senate as well. As the votes were tallied, Senator David Perdue, the Republican incumbent, was on the cusp of falling below 50 percent, which would trigger a runoff in January.
Georgia already faces a runoff for its other Senate seat, now held by a Republican, Kelly Loeffler. If Democrats were to win both, and Mr. Biden prevails in the presidential race, the Democrats could capture control of the Senate, with a bare margin of 50 seats, and the vice president casting a tie-breaking vote.
With Mr. Trump’s political path growing more precarious, his team turned to the courts, filing lawsuits and demanding a recount in Wisconsin.
The Trump campaign’s bid to stave off defeat stretched from the Supreme Court, where the campaign intervened in a case challenging Pennsylvania’s plan to count ballots received for up to three days after Election Day, to individual counties where the campaign showed a willingness to fight over even the smallest batch of votes.
The political tensions started to spill into the streets, with protests in Minneapolis, Seattle, Phoenix, Philadelphia, New York City and Portland, Ore.
While mostly peaceful, with chants demanding that every vote be counted, store windows were shattered in Portland as some protesters grappled with the police. In Minneapolis, demonstrators shut down a freeway and dozens were arrested.