But the barriers to voting posed by the pandemic have raised the stakes.
Voting by mail is the prime battleground. Thirty-four states and the District of Columbia allow excuse-free absentee voting, most likely ensuring that November’s election in those places will be conducted largely by mail if the pandemic persists. Many of the remaining states loosened mail-balloting rules for primaries, and some have moved to do so for November as well. But Republicans — led vocally by Mr. Trump — have insisted, without evidence, that loosening absentee ballot rules invites widespread fraud.
“We understand if people want to vote absentee, but there’s a process for that,” Ms. Harrington said. Easing rules can lead to errors, she said, citing reports that some ballots mailed to voters in Nevada’s primary wound up in apartment lobbies or the trash.
“That’s not the way a first-world country conducts elections,” she said.
Voting rights advocates note that some states vote almost entirely by mail with almost no instances of fraud. “This has nothing to do with the safety and security of the election,” said Sylvia Albert, the director of voting and elections for Common Cause. “It’s clear their intention is to limit access to the ballot for people who they think won’t vote for them.”
The vote-by-mail legal battles run the gamut of election rules. There are fights over whether to let voters vote absentee at all, whether to automatically mail them ballots or ballot applications, whether to relax witness requirements for absentee ballots and even over how ballots should be collected.
Democrats and voting rights groups have won their share of these disputes: In Nevada, a no-excuse absentee balloting state, the courts upheld the state’s plan to mail absentee ballots to all active voters over Republican objections. In Minnesota, another no-excuse state, Democrats persuaded a judge over Republican objections to suspend a requirement that absentee ballots be signed by a witness, a condition some voters could struggle to meet in a pandemic.
But Republicans have prevailed elsewhere. In Wisconsin, they went to the Supreme Court in April to thwart plans by the state’s Democratic governor to delay the primary election because of the coronavirus and allow further absentee balloting.
Another potential battleground, Texas, tightly restricts absentee voting by anyone under 65. The Republican-controlled government has blocked lawsuits by the Texas Democratic Party seeking to open mail balloting to all citizens, in part because of the pandemic.