Recall your last voting experience: chances are you were packed into a school cafeteria, shuttled along to a table where someone checked your name off a long list of registered voters, and you cast your ballot before rushing to work.

Until this Monday, in Ohio, if among the chaos of voting at peak hours in major elections, you were mistakenly directed to the wrong precinct at table 4 instead of your precinct at table 5 by a confused election worker, your vote could become a provisional ballot. That would mean it would likely be discounted because you voted in the wrong precinct without knowing you were doing so.

On Monday, a federal judge issued an injunction against the perennial swing state’s so-called wrong-precinct law (known to some as the “right church, wrong pew” rule), which stipulates that provisional votes cast in the wrong precincts can be discounted. According to the Advancement Project, a civil-rights group that filed the original suit against the state, 14,000 voters in Ohio had their ballots rejected in the 2008 election cycle due to the wrong-precinct rule.

Ohio is a state where every vote counts, making the ruling all the more significant for the upcoming presidential election: a recent Columbus Dispatch poll found President Obama and Mitt Romney deadlocked just two months ahead of the general election, each with 45 percent of the state’s eligible voters.

Rick Hasen, a professor of election law at UC Irvine and the author of The Voting Wars, called Monday’s decision “the most important ruling on voting rights we’ve had this election cycle.”

U.S District Judge Algenon L. Marbley, who halted the law, wrote in his decision that “recent experience proves that our elections are decided, all too often, by improbably slim margins—not just in local races…but even for the highest national offices. Any potential threat to the integrity of the franchise, no matter how small, must therefore be treated with utmost seriousness.”

Ohio Secretary of State Jon Husted, a Republican, told The Daily Beast the state most likely will appeal the ruling, meaning this chapter in this summer’s voting-rights saga could run up to Election Day in November. Husted defended the law, arguing that “a provisional ballot is a second chance when a voter has not taken their personal responsibility to prepare themselves to cast a correct ballot.”

But voting-rights experts say the rule is unfair and illogical. “If you have a polling place that has multiple precincts in it, and you go to the wrong table in the room, your vote will be discounted,” says Tova Wang, a senior democracy fellow at Demos, a think tank in New York. “That seems patently unfair and it happens all the time.”

“Any potential threat to the integrity of the franchise, no matter how small, must therefore be treated with utmost seriousness.”—Judge Algenon L. Marbley

“From a common-sense perspective, it seems quite unfair to reject a vote because a poll worker made a mistake,” says Dan Tokaji, a professor of election law at Ohio State University’s Moritz School of Law.

Hasen pointed to one example of a vote cast on Election Day 2010 in Ohio’s Hamilton County that ultimately may have been discounted because the poll worker sent the voter to the wrong table (PDF), thinking the voter’s house number—798—was an odd number and should be counted with other addresses in a different precinct.

The ruling comes at a particularly contentious moment for voting rights, as debate rages in other crucial swing states such as Pennsylvania—with its new law requiring voters to display identification—and Florida, over voter-ID laws critics are calling “voting purges.”

The issue of provisional ballots, at play in Ohio, is equally, if not more important, than the controversy over voter ID, says Wang: “Provisional ballots can swing the election, especially in a close race. The provisional ballot issue has been the sleeper problem of elections over the last few years.”