See this press release, which links to this report issued today by Project Vote and written by Lorraine Minnite. The press release begins:

Washington, DC – Widespread “voter fraud” is a myth promulgated to suppress voter participation, according to a new Project Vote report released this week. “The Politics of Voter Fraud” finds that fraudulent voting, or the intentional corruption of the voting process by voters, is extremely rare. Yet, false or exaggerated claims of fraudulent voting are commonly made in close electoral contests, and later cited by proponents of laws that restrict voting.