Barack Obama and John McCain have armies of volunteers to ring doorbells. They are also forming squadrons of lawyers.
Their mission: File challenges and be prepared 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 potential fights to come over ballot access in an election marked by unprecedented efforts to increase the number of voters in key states.
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 government databases.
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Much of the partisan disagreement is over enforcing a 2002 federal law 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 drivers' licenses or Social Security records.
In her successful Supreme Court petition, Brunner called the order a recipe for “disruption” and “chaos.”
Republicans contend the federal law requires record checks to counter fraudulent registration, which they say has been perpetrated by ACORN, the community activist network.
ACORN says bogus applications are only a tiny percentage of the new voters it registered, and it flags suspicious cases to election officials.