State Voter Identification Requirements: Analysis, Legal Issues, and Policy Considerations. Eric A. Fischer, Senior Specialist in Science and Technology; R. Sam Garrett, Specialist in American National Government; L. Paige Whitaker, Legislative Attorney. July 5, 2016:

“About 60% of U.S. voters live in the 33 states that require a voter at a polling place to produce an identification document (ID) before casting a ballot. Among those states, 20 permit voters without ID to cast a ballot through alternative means, such as signing an affidavit; 13 strictly enforce the ID requirement. The other 17 states and the District of Columbia have a range of non document requirements instead. Over the last two decades, the number of states requiring voter ID s has tripled. The stringency of those requirements is controversial. States var y substantially in the range of IDs accepted, the information they must contain, and the ease with which a voter can procure an ID. Although all states requiring voter ID accept a local driver’s license, no two states have the same overall requirements. Among states with voter ID laws, 20 require photographic identification (photo ID), while 13 permit a nonphoto ID. In addition, 8 states require ID for voters casting absentee or mail-in ballots.”