Early voting has begun in Iowa, one of the key swing states that could decide November's US presidential election.
The campaigns of President Barack Obama and Republican Mitt Romney are mobilising supporters to cast their ballots.
South Dakota, Vermont and Idaho have already begun in-person early voting, but Iowa is the first of the swing states to do so.
Most Americans will go to the polls on 6 November, now 40 days away.
In the last presidential election, Iowans cast 545,000 votes early, about 30% of the total ballots in the state, and awarded Mr Obama a solid majority.