COLUMBIA, S.C. -- More Democrats are concerned about the economy than the war, exit polls show in South Carolina show as presidential rivals Barack Obama, Hillary Clinton and John Edwards collided Saturday in a racially charged South Carolina primary.

Results | Candidates | Slideshow | Newsletter

South Carolina offered 45 Democratic National Convention delegates, as well as the campaign's first indication of Obama's political appeal in a state with a large black population.

Clinton hopes to become the first woman to occupy the White House, and Obama is the strongest black contender in history.

After playing a muted role in the earlier contests, the issue of race dominated an incendiary week that included a shift in strategy for Obama, a remarkably bitter debate, and fresh scrutiny of former President Bill Clinton's role in his wife's campaign.

Polls opened at 7 a.m. EST and election officials reported no problems with voting machines as there were in last week's GOP primary after one county's electronic machines failed to function properly.

"Everything's going smoothly," said state Election Commission spokesman Chris Whitmire.

Watch Economy, Exit Poll Says

Given three choices, half the voters in Saturday's primary said the economy was the most important issue facing the country -- up from 38 percent in the only other competitive Democratic primary to date, in New Hampshire on Jan. 8. About a quarter picked health care, comparable to New Hampshire. Only about one in five picked Iraq, down from 27 percent in New Hampshire.

The results are from a partial sample of 1,269 voters conducted by Edison Media Research and Mitofsky International in 35 precincts in South Carolina's Democratic primary. The margin of sampling error plus or minus 4 percentage points.

As in New Hampshire, three in four Obama voters said the most important quality in a candidate is that he can bring about needed change. Four in 10 Clinton voters said their priority was that a candidate has the right experience while nearly three in 10 picked change. Edwards scored highest on empathy -- at least half his voters said it was most important that the candidate "cares about people like me." Few voters said the candidate's electability was their top priority.

Asked whether their candidate's positions on issues or leadership and personal qualities were more important to their vote, six in 10 said issues.

Three in four voters said the country is ready to elect a black president and about as many said that about a woman. Somewhat more Clinton voters said the country is not ready to elect a black than Obama voters said the country wasn't ready to elect a female president.

After the contentious Democratic debate Monday night, three in four Obama voters said Clinton had attacked Obama unfairly and slightly fewer than half accused their own candidate of attacking Clinton unfairly.

Two-thirds of Clinton voters said Obama attacked her unfairly and nearly as many said she attacked him unfairly. Edwards voters were more likely than either of the other candidates' supporters to say both Clinton and Obama attacked each other unfairly.

Roughly four out of five voters said they would be satisfied if Clinton or Obama wins the Democratic nomination. Slightly more Clinton voters said they would be dissatisfied with Obama than vice-versa.

Slightly more Obama voters said Clinton would be more likely to be the eventual Democratic nominee than vice-versa.