Challenges at the polls, voter confusion and potential problems with provisional ballots in many key states are among the top Election Day concerns for voting rights groups and the presidential campaigns themselves.
Voting-rights advocates are particularly concerned about the tea party-linked True the Vote organization, which has pledged to dispatch thousands of monitors to polling places to guard against potential voter fraud.
Barbara Arnwine of the Lawyers Committee for Civil Rights Under Law says True the Vote has targeted African-American and Latino polling places.
True the Vote President Catherine Engelbrecht, however, rejects suggestions that the Houston-based group would be overly aggressive or issue false challenges.
The concern over poll monitors is only the latest in the legal and political battles over voter ID restrictions and other laws.