In a victory for Democrats, U.S. District Judge Susan K. Dlott issued a restraining order Wednesday night blocking local election officials from holding hearings on as many as 35,000 voter challenges brought by Republicans.

The GOP had challenged the eligibility of those voters because election mailings to them were returned by the post office. The Republicans alleged that the voters were improperly on the rolls as a result of mistakes or fraud committed by Democrat-allied groups.

The Democrats said the challenges violated federal law and accused the GOP of attempting to discourage eligible voters from going to the polls on Election Day.

The case is among a growing number of legal battles raging in Ohio and across the country as both parties brace for another contentious presidential election. The fight is especially intense in closely contested swing states like Ohio.

Dlott did not issue a formal ruling explaining her decision.

She will hold another hearing on the issue Friday. Her ruling applies only to six Ohio counties where challenges were filed: Cuyahoga, Franklin, Lawrence, Medina, Scioto and Trumbull. But other boards are expected to follow the ruling.

Republicans dropped their challenges to voters in Hamilton County because of a computer glitch that caused them to challenge hundreds of eligible voters.

Ohio Secretary of State J. Kenneth Blackwell told the state's attorney general Wednesday that he did not wish to appeal the ruling.

Democrats praised Dlott's ruling, saying it proves they were right about the GOP's motives.

"The Republican assault on tens of thousands of Ohio voters was an unprecedented effort to intimidate voters, especially minorities," said David Sullivan, director of the Democrats Voter Protection Program. "But it has backfired."

Democrats criticized the challenges as sloppy and said the GOP was attempting to pre-emptively disqualify thousands of potential voters.

But Republicans said there's ample anecdotal evidence of voter registration fraud.

"We think it will result in longer lines, more confusion and frustrated voters on Election Day," said Mark R. Weaver, a lawyer for the Ohio Republican Party. "This is the week we should have been clarifying the questionable registrations. Because of the judge's rulings, that can only take place on Election Day."

The GOP plans to place 3,600 challengers at Ohio polling places next Tuesday under an Ohio law allowing any voter to challenge the eligibility of any other voter.

Blackwell issued a directive this week to boards of elections that would allow those challenged to cast a provisional ballot, allowing election officials more time to resolve the dispute before the ballot is counted 10 days later.

But the Republicans also wanted hearings on challenged voters to happen before Election Day.

Timothy M. Burke, chairman of the Hamilton County Democratic Party, said it would have been unfair and logistically impossible for the board to hear so many challenges before the election.

In a separate but related elections case filed Wednesday, two long-time civil rights activists in Cincinnati asked Dlott to grant a restraining order to protect the voting rights of African-Americans on Election Day.

Marian and Donald Spencer accused Republicans of assigning "challengers" to polling places in predominantly African-American precincts in order to "delay, deter and deny" access to the polls.

The system of election challengers has been available for years in Ohio.

Under Ohio law, challengers are permitted to observe activity in polling places and to challenge voters' eligibility if they believe there is a problem. Each party may have one challenger in each polling place.

In the past, neither party has posted many challengers. But in the wake of the 2000 presidential election, both parties now intend to deploy hundreds.

The Spencers argue that GOP officials will aggressively challenge voter registrations in African-American precincts, which lean heavily to Democrats.

They asked Dlott to take steps to ensure that doesn't happen and, if necessary, to bar all challengers. Dlott did not rule Wednesday.

E-mail dhorn@enquirer.com and gkorte@enquirer.com