NEW YORK - Welcome to the first presidential election in which nearly every state must have a list of every registered voter. Here's the catch: If your name isn't on it, you may have trouble casting a ballot in this historic race for the White House.
The lists have already caused problems in New Mexico, Arizona, and California, where people waited hours to choose a presidential nominee only to find they weren't listed as registered voters - or they weren't listed in the party of their choice.
Tomorrow, when people line up in the crucial states of Ohio and Texas, election observers fret that similar snafus will confuse and delay primary vote counts.
"It could be the sleeping giant in terms of voting problems," said Larry Norden of the Brennan Center for Justice at New York University's law school, which monitors election issues.
The problems stem from a federal law that was supposed to deter voter fraud. Under the Help America Vote Act, every state was required to have a computerized database listing all registered voters. The deadline was 2006, which several states missed. This year marks the first time the lists are being used in presidential contests, and every state except North Dakota (which has no registration system) has some interim or permanent system in place.
But there is great confusion about what to do if a voter's name is missing, or shows up under the wrong party affiliation, election advocates say.
In states such as New Mexico, where Super Tuesday caucuses were plagued by long lines and registration issues, it took nine days to tally votes. Part of the problem stemmed from an avalanche of so-called provisional ballots - which take longer to count - given to voters for a variety of reasons, including being dropped from registration lists.
In California, the Super Tuesday final tally has yet to be certified because of large numbers of impromptu ballots cast by voters whose names weren't on the list, as well as other poll problems.
The voting law was designed to produce accurate lists of eligible voters that could be coordinated with other government databases, including driver's license and Social Security rolls.
Some election officials interpreted those requirements to mean that registration applications should be denied when they don't match government data.
In Florida, the state NAACP chapter and others sued election officials, saying more than 14,000 people, most of them minorities, have had their registrations wrongly denied or delayed since 2006.
According to the federal lawsuit, many of the discrepancies were caused by transposed numbers, and confusion over minority names.
In December, a federal judge ordered election authorities to stop enforcing the two-year-old law, saying there is proof that it has resulted in "actual harm to real individuals." The case is on appeal.
Ohio and Texas have had problems getting their registration databases up and running, creating fears that it may take days to tally votes from these contests.
In the last presidential election, nearly 3 percent of Ohio voters were forced to cast provisional ballots because of registration questions after waiting in lines for as long as 14 hours. Those paper votes helped prolong the final tally by more than a month.
Several Texas counties have called the state's database unreliable. Some have opted for privately run databases, but state officials say their system has been fixed and should run smoothly tomorrow.