Stephen Ansolabehere, Massachusetts Institute of Technology

The Help America Vote Act hit a nearly fatal snag during the final stages of congressional negotiations over the bill in 2002. The problem? Voter identification requirements. Many conservatives in Congress insisted on the inclusion of a requirement that voters show photo identification, and many liberals, especially the Congressional Black Caucus, saw this as a deal killer. Ultimately, the two sides reached a compromise that applied the rule to first time voters, but the battlelines over this question were drawn and they remain in place today.