Trump's campaign asked to intervene in a pending US Supreme Court case over whether Pennsylvania, another key state that was still working its way through hundreds of thousands of mail-in ballots, should be permitted to accept late-arriving ballots sent by Election Day.
His campaign also said it would request a recount in Wisconsin and added that it had filed lawsuits in Michigan and Pennsylvania seeking to halt vote counting, arguing that officials had failed to allow fair access to counting sites.
Taken together, Trump's legal maneuvers amounted to a broad effort to contest the results of an election yet to be decided a day after millions of Americans went to the polls during the coronavirus pandemic that has upended daily life. They followed Trump's early-morning attacks on the integrity of the vote, as the president falsely claimed victory and suggested without substantiation that Democrats would try to steal the election.
Biden said: "Every vote must be counted. No one's going to take our democracy away for us, not now, not ever. America's come too far, America's fought too many battles, America has endured too much to ever let that happen."
Trump is trying to avoid becoming the first incumbent US president to lose a re-election bid since George H.W. Bush in 1992.
Biden won Michigan by 67,000 votes, or 1.2%, while he was ahead in Wisconsin by just over 20,000 ballots, or 0.6%, according to figures from Edison Research, which projected Biden as the winner in Michigan. Several news outlets projected Biden as the winner in Wisconsin, though Edison did not, citing the pending recount.
Wisconsin law allows a candidate to request a recount if the margin is below 1%, which the Trump campaign immediately said it would do.
In response to the Michigan lawsuit, Ryan Jarvi, a spokesman for the state attorney general, said the elections had been "conducted transparently".