The undecided presidential election entered a new phase on Wednesday as former Vice President Joseph R. Biden Jr. was declared the winner of Michigan and Wisconsin, two key swing states that President Trump won four years ago.
The Trump campaign, whose path to victory was narrowing, said that it would seek a recount in Wisconsin and then announced that it had taken legal action seeking to halt the vote count in Michigan, one of a flurry of lawsuits that included joining an action challenging the extension of ballot deadlines in Pennsylvania and filing another seeking to segregate late absentee ballots in Georgia.
The Trump campaign’s string of challenges came as the president found himself with few paths remaining to winning the 270 electoral votes needed to be re-elected. By Wednesday afternoon, Mr. Biden was holding slim leads in several key states which, if the trend continues, could propel him to the critical Electoral College threshold and the presidency.
The lingering uncertainty of the 2020 campaign was perhaps unsurprising in an election with record-breaking turnout where most ballots were cast before Election Day but many could not be counted until afterward.
Mr. Trump’s chances of winning a second term depended on his ability to hang on to his leads in states like Georgia and in Pennsylvania — where Mr. Biden has been narrowing the gap as vote counting progresses — and on overtaking Mr. Biden in one of the states where he is currently ahead.
With millions of votes yet to be counted across several key states — there is a reason that news organizations and other usually impatient actors were waiting to declare victors — Mr. Biden was holding narrow leads in Arizona and Nevada. If he can hold those states, the former vice president could win the election even without Pennsylvania, which has long been viewed as a must-have battleground state.
“I’m not here to declare that we’ve won,” Mr. Biden said in a speech Wednesday afternoon in Wilmington, Del., “but I am here to report that when the count is finished, we believe we will be the winners.”
Even before the Wisconsin race was called, the Trump campaign said that it would request a recount. Under Wisconsin law, a recount can be requested if the margin between the top two candidates is less than one percentage point.
Bill Stepien, Mr. Trump’s campaign manager, said in a statement that “the president is well within the threshold to request a recount and we will immediately do so.”
Mr. Stepien later claimed that the Trump campaign had not been given “meaningful access” to several counting locations in Michigan, and that it had a filed suit in the Michigan Court of Claims to halt counting until access was granted. Shortly after that he announced that the campaign would intervene in Pennsylvania. Later in the evening, the campaign said it was filing suit in Georgia seeking to get counties to separate late-arriving ballots from the rest.
Taken together, the legal actions threatened to slow the counting in states where Mr. Trump was projected to lose or in danger of losing.
One source of Mr. Biden’s resilience lies in the nature of the votes still to be counted. Many are mail-in ballots, which favor him because the Democratic Party spent months promoting the message of submitting votes in advance, while Mr. Trump encouraged his voters to turn out on Election Day. And in Pennsylvania, many of the uncounted votes are from populous urban and suburban areas that tend to vote heavily for Democrats.
Four years ago, Michigan provided one of Mr. Trump’s most surprising victories and helped him take back the Northern industrial states that had favored Democrats in presidential elections since the 1990s. In this election, Mr. Trump’s popularity took a serious hit with the coalition of white voters — independents, those who had an unfavorable view of him but supported him anyway, people with and without college educations — that helped secure his win in Michigan in 2016.
Even in Pennsylvania, where Mr. Trump had run up a daunting lead of roughly eight percentage points as of Wednesday afternoon, Mr. Biden had a plausible shot of catching up. Pennsylvania’s secretary of state said there were more than 1.4 million mail-in ballots still to be counted, and those votes are expected to heavily favor Mr. Biden.
Mr. Trump held leads in North Carolina and Georgia, and his campaign expressed hopes that his early Pennsylvania lead could withstand an influx of mail-in ballots for Mr. Biden. Then, if Mr. Trump was able to retake the lead from Mr. Biden in Arizona or Nevada, which has gone Democratic in recent elections, he would have a path to a second term.
Early Wednesday, Mr. Trump prematurely declared victory and said he would petition the Supreme Court to demand a halt to the counting. Mr. Biden urged his supporters — and by implication, Mr. Trump — to show patience and allow the process to play out.