The nation's first trial to challenge punch-card balloting since the Florida fiasco four years ago opened Monday with a lawyer arguing that even isolated malfunctions in Ohio could change the November election results in this swing state.

Paul Mokey, a lawyer for the American Civil Liberties Union of Ohio, argued in federal court that the state's punch-card machines are not uniform and that in several counties they are antiquated and do not allow voters to correct mistakes. The ACLU wants punch-card ballots declared unconstitutional.

Lawsuits filed by the ACLU against several other states have been settled with agreements to eliminate such ballots.

In Ohio, the ballots are used in 69 of 88 counties, representing nearly 73 percent of registered voters. In the 2000 presidential election, the ballots of nearly 94,000 Ohio voters were rejected.

Mokey noted that Cincinnati's Hamilton County, which had aging punch-card machines in the 2000 election, discounted 2,916 ballots with more than one candidate selected for president.

"In a close election such as that is predicted in Ohio this fall, those 2,916 votes could make the difference," Mokey said.

Punch-card balloting gained attention during the 2000 presidential election in Florida, where problems with the ballots led to 36 days of legal wrangling and recounts, until George W. Bush was declared the winner of the state, and thus the White House, by 537 votes.

Bush won Ohio by a larger margin, but in a recent poll of Ohio voters by the American Research Group, he was tied with Democrat John F. Kerry.

Rich Coglianese, an attorney for the state, said that there is not enough time to replace punch-card systems before the Nov. 2 election and that the state wants to be sure electronic voting machines are secure before using them statewide.

"The worst thing the state of Ohio can do is implement new voting machines with problems," he said.

The ACLU argues that punch cards are more likely to go uncounted than votes cast with other systems, and that use of the ballots violates the rights of black voters, who mostly live in punch-card counties.

Martha Kropf, a professor of political science at the University of Missouri at Kansas City, testified for the ACLU that precincts with higher numbers of black residents have more cases of votes for multiple presidential candidates or none at all.

Coglianese said Ohio would show that there is no discrimination based on voting equipment.

Dana Walch, director of election reform at the Ohio secretary of state's office, acknowledged problems with punch cards and said there are plans to replace them by 2005 with machines that alert voters if they make a mistake.

Even if punch-card systems cannot be replaced before November, the ACLU still wants the judge to rule them unconstitutional. The ACLU has not endorsed an alternate system.

U.S. District Judge David D. Dowd Jr. agreed to the ACLU's request to hold further hearings to determine possible remedies if he rules in the group's favor.