His top lieutenants shared that assessment.
During a marathon Zoom session in May, after the campaign’s first major round of polling in the general election, Mr. Biden and his high command spent hours poring over the electoral map. By the end, they had hammered out their priorities: They would focus on three Great Lakes states Mr. Trump flipped in 2016 — Wisconsin, Michigan and Pennsylvania — plus Arizona, Florida and North Carolina. The campaign was skeptical of its chances in Florida and saw two other Sun Belt states, Georgia and Texas, as intriguing — but difficult and expensive to compete in.
When Mr. Biden and Ms. Harris returned to the campaign trail, that map guided their activities and their advertising strategy. They lunged at a few longer-shot targets, sending Ms. Harris on a last-minute trip to Texas, while Mr. Biden returned to Ohio, where polls showed him being competitive. Neither state wound up being close on election night.
More fruitful was an aggressive late play for Georgia, a rapidly diversifying state where suburban voters appeared to be swinging hard toward Democrats. In October, Mr. Biden’s pollster, John Anzalone, determined that the former vice president had a better chance to win there than in North Carolina and even Florida, and Mr. Biden embarked on his trip to Atlanta and Warm Springs. Ms. Harris visited the state repeatedly, and on the eve of the election the campaign decided to send former President Barack Obama to Georgia rather than North Carolina to make one last push there.
As the results began coming in on Tuesday, a tense mood took hold across much of the Biden campaign. In the first states to report, Florida and North Carolina, Mr. Trump was faring several points better than Democratic polling had forecast, and considerably ahead of most surveys conducted by the media.
The Biden campaign publicly projected composure, in contrast to Mr. Trump’s erratic behavior on Twitter and during late-night remarks from the East Room. Greg Schultz, Mr. Biden’s former campaign manager during the Democratic primaries, held a call with key supporters to offer reassurance, insisting that the early returns in the suburbs of Ohio were a good omen for the nearby swing states. But to some agitated listeners it was not a convincing presentation.
Mr. Biden’s inner circle grew increasingly unnerved as the night wore on and it became clear that the president was running stronger than expected. Jill Biden, former Senator Christopher Dodd of Connecticut and an array of Biden advisers telephoned Democrats around the country to learn more about the vote count and whether Mr. Biden was in danger of losing.
Within a matter of hours, Mr. Biden’s fortunes had improved as the big cities of the North reported their votes. It would take until Saturday, when Pennsylvania was called in his favor, to confirm that Mr. Biden had won more than the 270 Electoral College votes required to claim the presidency. The Blue Wall was standing again for Democrats, and Mr. Biden could also prevail in the once-red states of Arizona and Georgia.