Ahead of the vote tomorrow, recent polls in North Carolina have suggested that Amendment One, which would introduce a constitutional ban on equal marriage, and outlaws even civil unions, looks set to pass.

According to US media reports, supporters of the amendment are driving a record turnout in early voting, which is also thought to spell trouble for Mr Obama’s campaign for re-election in the November elections.

The vote comes after months of bitter campaigning by both the religious right and by gay rights activists, but it is thought that the endorsement of the amendment by the evangelist Billy Graham boosted the anti-equality cause considerably. Mr Graham’s letter of support for the amendment appeared in newspapers around the country. The amendment also saw statement of support from Newt Gingrich, who has since bowed out of the presidential race.

Public Policy Polling released its findings last week according to which the amendment is likely to pass with a 14% majority, 55% for the measure and 41% against. That the pollster in this case is liberal-leaning is what worries gay rights activists the most. Equally, polls have repeatedly found that when the significance of the amendment, that it bans all civil unions outside heterosexual marriage, is revealed, people were the likelier to vote against the measure.

The results of the poll are expected to be also a measure of Mr Obama’s popularity in the state, which narrowly gave him the victory in 2008.