President Barack Obama
U.S. President Barack Obama's support for same-sex marriage has had little effect on people's voting plans, according to recent polls.
When weighed against concerns such as the economy, few voters are likely to make their choice for president on the basis of the candidates' positions on same-sex marriage.
Recent polls by Gallup, Pew and the Washington Post/ABC News have found increasing public support over the years for gay marriage in principle.
The Post/ABC poll found 53 per cent of Americans said gay marriage should be legal.
As recently as six years ago, that figure was 36 per cent.
Thirty states have constitutional amendments banning same-sex marriage; some of those also prohibit civil unions and other approaches that grant legal rights to such couples.
Twelve states permit civil unions.