Joseph R. Biden Jr. started election night with many paths to 270 electoral votes, but by Wednesday morning President Trump had won Florida, Ohio and Texas and was within striking distance of winning North Carolina.
That left a diminished but still significant number of ways by which Mr. Biden could prevail, mostly clustered around recapturing Michigan, Wisconsin and Pennsylvania, the once-reliable “blue wall” states that Mr. Trump toppled four years ago.
One alternate path still available for Mr. Biden: winning both Arizona and Georgia, Sun Belt states where he appears in good shape with tens of thousands of votes left to be counted.
Mr. Biden is on track to win Arizona, the first flip of a 2016 Trump state after a succession of near, and not-so-near, misses in other battlegrounds.
If Mr. Biden prevails in Georgia, he can reach 270 electoral votes while losing Pennsylvania and Michigan or Wisconsin.
Or he could become president simply by winning back Michigan, Wisconsin and Pennsylvania.
In Georgia, where Mr. Trump held a substantial lead with about 80 percent of the vote counted, a leak at a processing center in the central part of the state halted the tabulation of ballots for Atlanta and its suburban counties, which are seen as Democratic strongholds.
Well over half the vote remains left to count in DeKalb County, a heavily Democratic suburb of Atlanta, making the race a tossup heading into Wednesday morning.
Mr. Biden, appearing briefly before his supporters in Wilmington, Del., early Wednesday, said he was “feeling real good about Wisconsin and Michigan” and predicted a win in Pennsylvania, a central battleground that is notorious for its sluggish counting of ballots.
“We believe we are on track to win this election,” he said.
Mr. Trump’s victories in Florida, Ohio and Texas did not create a new path for him so much as close off new shortcuts by which Mr. Biden could have claimed victory on Election Day. In remarks made early Wednesday from the White House, the president was adamant that he would hold onto Georgia, North Carolina, Michigan, Wisconsin and Pennsylvania — all states with significant percentages of ballots left to count.
“We don’t need all of them” to win, he said.
His last chance for a flip is Nevada, which was expected to be a tight race, but one generally favoring Mr. Biden.
Otherwise, Mr. Trump’s path to winning a second term depends on holding onto the battleground Great Lakes states he won in 2016 and on retaining Georgia.