Despite limited evidence of fraud, 11 states approved new rules over the past two years requiring people to provide identification when they vote.
Some laws mirror those in Indiana and Georgia, the first to adopt strict ID rules.
An Associated Press review of absentee ballots from those states found that more than 1,200 votes were tossed during the 2008 general election.
The numbers suggest that the legitimate votes rejected by the laws are far more numerous than the cases of fraud that the rules are trying to prevent.
Thousands more votes could be in jeopardy for this November, when more states with larger populations are looking to have similar rules in place.
More than two dozen states have some form of ID requirement.