Many of the approximately 300 lawsuits filed this year over voting rules have been settled. But some key ones remain unresolved and court decisions could still reshape how voting is conducted in some crucial states.
The flurry of last-minute legal action comes as more than 5 million people have already cast ballots early or by mail, causing some confusion over what voters have to do to ensure that their votes count.
On Monday, the U.S. Supreme Court ordered that voters in South Carolina need a witness signature on their absentee ballots. But the high court said the order did not apply to tens of thousands of voters in the state who have already voted, because a lower court ruled last month that the witness signature was not required.
The case is only one example of the legal whiplash voters are experiencing this year, as political parties, campaigns and interest groups take their differences over voting to the courts. In South Carolina, Democrats argued that the witness requirement was unnecessary and burdensome, especially during a pandemic. Republicans argued that the requirement discourages voter fraud.
Several other important cases could end up before the Supreme Court before Election Day.
Republicans have already asked the high court to block a recent decision by Pennsylvania's Supreme Court that would allow absentee ballots to be counted if they're received up to three days after Election Day, as long as they're mailed by Election Day.
Democrats and state election officials argue that this deadline extension is needed to protect voters against possible mail delays. But Republicans say the state Supreme Court overstepped its authority and that this a decision for the state legislature to make.
Other cases that could wind up before the Supreme Court include one in Wisconsin, where Republicans are fighting a federal court ruling allowing ballots there to be counted up to six days after Election Day.
Alabama officials are also trying to block a recent federal court decision that would waive that state's identification and witness requirements for absentee voters who are at high risk of contracting COVID-19. Alabama Secretary of State John Merrill said the state will seek relief from the Supreme Court because "we believe that it's federal judicial overreach and ... a legislator in a robe" trying to override state voting laws.
Several other important cases are working their way through the court system. Democrats and voting rights groups are challenging a recent decision by Texas Gov. Greg Abbott to limit the number of ballot drop-off sites to only one per county.
Republicans and Democrats are in court in Iowa fighting over whether tens of thousands of absentee ballot request forms are valid if most of the information was filled out in advance by county election officials.
The political parties are also at odds over how much time Arizona voters will have to fix signature problems with their ballots. A similar fight is being waged in North Carolina over how absentee voters can correct ballot mistakes. Voting rights groups are also challenging a requirement in Missouri that some voters need to have their mail-in ballots notarized.
Such vote-by-mail requirements have become more significant — and controversial — this year because of the large number of voters who are expected to cast their ballots by mail. A recent NPR analysis found that more than half a million absentee ballots were rejected in this year's primaries alone because of errors and missed deadlines.
With so many cases still up in the air, legal experts say it's difficult to tell whether Democrats or Republicans are coming out ahead. Democrats have won numerous victories — including fending off a Republican effort to prevent Nevada from automatically sending out ballots to all registered voters.
But Democrats have also had some of their earlier wins overturned. The South Carolina witness requirement is the most recent example. Republicans have been successful in a number of cases, including one to require felons in Florida to pay off all fees and penalties before they can vote.
"I would say Democrats and voting rights group had some important victories, but on those cases that made it up the food chain, they have tended to do not as well," said Rick Hasen, an election law expert at the University of California, Irvine.
Hasen thinks such victories could be even rarer in the weeks ahead because courts are reluctant to make changes in voting rules too close to an election. "Any kind of last-minute changes that expand voting rights coming now are going to have a really tough road as they go up the appellate process," he said.
How such cases are decided could prove crucial after the election, when potential legal challenges to the outcome might end up before the Supreme Court. President Trump has already said that he thinks that will happen.
Alabama Secretary of State Merrill this week also released a letter, signed by a number of Republican secretaries of state, that calls for swift Senate confirmation of Trump's Supreme Court nominee, Judge Amy Coney Barrett, to ensure that all the seats on the high court are filled by Election Day.
"In the case an election issue is challenged in court, America cannot afford a tie vote," they wrote Senate Judiciary Committee Chair Lindsey Graham, R-S.C.
Justin Levitt of Loyola Law School is more optimistic such an outcome can be avoided. The former Justice Department official thinks one benefit of all the current litigation is that it reduces the chance of a legal challenge after Election Day revolving around such questions as whether ballots received after Election Day can be counted.
"The fact that the courts have weighed in on that issue now means it's far less likely to want to weigh in on that issue after Election Day. And that's true for a lot of the different claims that have been pressed so far about which ballots are legitimate and which aren't," he said.