If voters have problems casting ballots anywhere in the nation, they can call a toll-free Election Protection Coalition hot line set up to report issues: (866) OUR-VOTE, or (866) 687-8683. EFF is a member of the coalition, which includes the People for the American Way Foundation, the National Association for the Advancement of Colored People, and the Lawyers' Committee for Civil Rights Under Law.

Problems could include hardware that doesn't properly record or cast ballots, machines that switch votes to other candidates on their electronic summary screens, or ones that reboot or crash as people attempt to vote. "Don't let concerns about the machines keep you from the polls," Zimmerman said. "If you have concerns [or problems voting}, the only way they're going to be fixed is if you let us know about it."

Courtenay Strickland Bhatia, president of San Francisco-based VerifiedVoting.org, a nonprofit, nonpartisan lobbying group that supports reliable and publicly verifiable elections, said problems are likely to affect states with close races, histories of past election problems and where lots of new e-voting machines are being introduced.

"This is the largest shift in voting equipment in our nation's history," Bhatia said. That means balloting will require stepped-up efforts by local elections officials, poll workers and voters to make sure they go smoothly. "We need citizens watching," she said.

A key problem, Bhatia said, is that because many areas are using e-voting machines that lack a paper trail, problems that are reported might not be properly checked out. That lack of records means "that the problems we see on Election Day will be the tip of the iceberg," she said.