"This is something that fits into a larger battle between the left and right over our voter rules," says Richard Hasen, author of a new book on the subject, called "The Voting Wars."
"What you see are liberal groups ... looking to enforce the pro-voter provisions of the National Voter Registration Act," the 1993 law also often known as the motor-voter act, say Mr. Hasen, who is a professor of law and political science at the University of California, Irvine. Conservatives, by contrast, tend to seek enforcement actions that purge voter rolls, such as weeding out people who are ineligible because they aren't US citizens.
Republicans have stirred Democratic anger in some states, for instance, with new laws requiring photo ID at the voting booth.
This pattern reflects both political calculations and ideological differences between the parties. In general, political analysts say Democratic candidates for office get a leg up when voter rolls are enlarged.
The results of one new survey, for example, suggest that President Obama could coast to reelection if he could generate higher turnout among Americans who are unlikely to vote – not because they aren't eligible but because they feel too busy or apathetic.
Beyond calculations of political gain, the "voting wars" that Hasen tracks are also about philosophical differences between the parties.
Democrats tend to emphasize the political positives of getting more eligible Americans to vote, while Republicans emphasize the civic virtue of minimizing vote fraud. Hasen sees room for the US to improve on both fronts, compared with other advanced nations that achieve both higher turnout and more careful management of the process.