Barack Obama and John McCain have a litigation game plan to accompany their election strategy.

Both candidates have armies of volunteers to ring doorbells and get voters to the polls. They are also forming squadrons of lawyers who are filing challenges and preparing in case Election Day doesn't settle the contest for the White House.

Legal battles unfolding in Ohio, Indiana and Wisconsin provide fresh evidence of the potential fights over ballot access in an election marked by unprecedented spending to increase the number of voters in strategically important states.

The millions of dollars that have been poured into registration drives have yielded millions of new voters across the country. Those same efforts have generated heated battles in both parties, with cries of voter fraud and intimidation that may threaten the integrity of the election.

Election officials are braced for huge turnout and the problems it could create with long lines, malfunctioning machines and challenges to voters.

Already, the U.S. Supreme Court has handed Ohio Democrats a victory, dissolving a court order obtained by Republicans to force state officials to release the list of 200,000 new voters whose names or addresses don't match the information in government databases.

Democrats accused Republicans of trying to improperly disqualify voters.

In Florida, Democratic corporate lawyer Charles H. Lichtman has assembled almost 5,000 lawyers to monitor precincts, assist voters turned away at the polls, and litigate any disputes that can't be resolved out of court.

"On Election Day, I will be managing the largest law firm in the country, albeit for one day," said Lichtman, 53, of Fort Lauderdale, a veteran of the five-week election recount in 2000.

Obama's lawyers also have pressed allegations that Michigan Republicans planned to use mortgage-foreclosure lists to challenge voters. The case was settled yesterday when both parties agreed not to use foreclosure lists to challenge voters. In Indiana, labor unions allied with the Democratic nominee are battling a Republican chairman over early voting in the state's second-largest county.

Much of the partisan disagreement is over enforcing a 2002 law that Congress enacted to help states prevent a Florida-type recount by requiring election officials to set up database checks to purge voters.

Ohio's Republican Party obtained a court order directing Jennifer Brunner, Ohio's secretary of state, to give county election officials the lists of new voters whose names didn't match driver's licenses or Social Security records.

In her successful Supreme Court petition, Brunner called the order a recipe for "disruption" and "chaos" as the state prepares for a presidential vote that polls of Ohio voters predict will produce another razor-thin margin.

Database checks are not "a litmus test" for the right to vote, she said in a statement announcing the appeal.

Republicans contend that the federal law requires records checks to counter fraudulent voter registration, which they say has been perpetrated by a nationwide network of community activists known as ACORN. Republican nominee McCain has cried foul over the drive by ACORN to register 1.3 million voters this year.

"They're registering the same person at different addresses," said Sean Cairncross, the Republican National Committee's chief counsel. "They're registering people at vacant lots" as well as "deceased individuals."

ACORN said that bogus applications were only a tiny percentage of the new voters it registered, and that it flags suspicious cases to election officials.

On Oct. 2, Ohio Republicans won a separate court fight with Brunner over absentee ballots cast by McCain supporters. The state's Supreme Court countermanded Brunner's order that local election boards reject the ballots if the applicant hadn't checked a box indicating he or she was a "qualified voter" when submitting the absentee ballot.

The McCain campaign wouldn't say how many lawyers it has deployed or how it was preparing for possible court fights. "We are not jumping to conclusions that litigation efforts are going to be widespread," said Ben Porritt, a McCain spokesman.

Hayden Dempsey, a Tallahassee lawyer who chairs Lawyers for McCain in Florida, said his party isn't "trying to lawyer up nearly so much as the Democrats."