There has been heavy voter turnout in the South Carolina Democratic Primary with Senator Barack Obama leading in most opinion polls.
Barack Obama is leading rival Hillary Clinton in polls and is counting on support from the sizable African-American population there, which is estimated to comprise almost half of Democratic voters.
The latest Zogby poll shows Mr Obama with a 41% to 26% edge over Mrs Clinton in South Carolina, with John Edwards in third place with 19%.
Voter turnout was heavy soon after polls opened at 12pm Irish time, with long lines at polling places reported in early morning balloting.
Record turnout of more than 300,000 is expected in the first Democratic primary in the South.
Results are expected early on Sunday morning.
‘I am absolutely convinced that we can win here, and we can win anywhere in the country,’ Mr Obama said at a late-night rally in Columbia that capped a week spent campaigning heavily across the state.
After two consecutive losses, in New Hampshire and Nevada, Mr Obama needs a win today if he hopes to head into the 5 February ‘Super Tuesday’ contests in 22 states with a realistic chance of victory.
Senator Hillary Clinton is running closely behind and has been joined in her campaign by her husband Bill Clinton and daughter Chelsea.
The South Carolina campaign has been marked by sharp exchanges between the Clinton and Obama camps.
