Jan. 26 (Bloomberg) -- Illinois Senator Barack Obama won the South Carolina Democratic primary by a more than 2-to-1 margin over New York Senator Hillary Clinton, claiming a crucial victory in his race for the party's presidential nomination.

``After four great contests in every corner of this country, we have the most votes, the most delegates, and the most diverse coalition of Americans that we've seen in a long, long time,'' Obama told a cheering crowd of supporters in Columbia, South Carolina.

With about 98 percent of the vote counted, Obama had 55 percent support to Clinton's 27 percent and Edwards's 18 percent. Obama, 46, and Clinton, 60, each have won two of the first contests in the nomination race.

Obama's victory gives him momentum as he competes with Clinton in the Feb. 5 round of voting involving 22 states, including California, Illinois and New York. Obama was leading in state polls ahead of today's primary, and Clinton spent much of the week campaigning outside South Carolina.

``There is now a two-person race,'' said Norm Ornstein, a scholar at the American Enterprise Institute in Washington. Obama ``has an equal claim on the nomination,'' he said.

Endorsement

Obama tonight was endorsed by Caroline Kennedy, the daughter of the late President John F. Kennedy. In an article published on the Web site of the New York Times, Kennedy wrote that Obama could inspire Americans ``the way people tell me my father inspired them.''

Obama, who's vying to become the nation's first black president, got a boost from black voters who made up about half of those casting ballots today, according to exit polls cited by CNN. He overcame an initial swing toward Clinton among those voters, who in the past gave strong support to her husband, former President Bill Clinton.

``The choice in this election is not between regions or religions or genders; it's not about rich versus poor, young versus old; and it is not about black versus white,'' Obama said.

More than 532,000 people turned out to vote in South Carolina, almost double the number who voted in the 2004 Democratic primary and 100,000 more than voted in the Republican contest a week earlier.

Clinton released a statement saying she had called Obama to congratulate him. ``We now turn our attention to the millions of Americans who will make their voices heard'' in the primaries ahead, Clinton said in the statement.

Edwards congratulated Obama and vowed to move on to the Feb. 5 contests.

Exit Polls

Obama carried 81 percent of the black vote to Clinton's 17 percent, according to exit polls cited by Fox News, CNN and MSNBC. Obama also got 24 percent of the white vote, with Clinton and Edwards dividing the remainder, the exit polls showed. Exit polls cited by MSNBC showed that Obama also won 49 percent of the state's young voters, aged 18 to 29.

Both Clinton and her husband drew criticism in the past few weeks from black leaders who said they injected the issue of race into the campaign. Obama accused Bill Clinton, who has been campaigning for his wife across South Carolina, of making statements that ``aren't supported by the facts.''

Obama directed criticism at some of the tactics of his chief rival in his victory speech, without mentioning her name.

``We are up against decades of bitter partisanship that cause politicians to demonize their opponents instead of coming together to make college affordable or energy cleaner,'' he said. ``It's the kind of partisanship where you're not even allowed to say that a Republican had an idea - even if it's one you never agreed with.''

`Say Anything'

Repeating a theme he used in campaign commercial targeting Clinton, Obama said his campaign is ``up against the idea that it's acceptable to say anything and do anything to win an election.''

Bill Clinton's campaigning may have hurt his wife in the state, according to exit polls posted by CNN. Six out of 10 voters said his campaigning was ``important'' to their decision, and 47 percent of those voters went for Obama, CNN said.

The former president also drew fire today by comparing Obama's South Carolina victory to that of another black politician who won the state's Democratic presidential primaries in 1984 and 1988. ``Jesse Jackson won South Carolina twice,'' Clinton said, according to the New York Times.

`Implicit Comparison'

The comment ``just compounds'' the negative attacks on Obama that turned off South Carolina voters, said Merle Black, an expert on Southern politics at Emory University in Atlanta. ``The implicit comparison is that Jackson won but he didn't win the nomination,'' Black said. ``That is just another round of trying to devalue what Obama has achieved.''

In South Carolina, thousands of supporters waiting for Obama to speak began booing when a video popped up of the former president speaking in Independence, Missouri.

The highest-ranking black politician in South Carolina, U.S. Representative James Clyburn, said last week that the former president ``needs to chill a little bit.''

In an interview with Bloomberg Television tonight after the networks predicted an Obama win, Clyburn said the results were ``an example of what we need to do to get beyond race.''

South Carolina has 54 Democratic delegates to the Democratic nominating convention, including 45 awarded to the candidates based on today's results. Obama adviser Bill Burton said the campaign calculates they will emerge with 25 delegates and that Clinton would garner 12, and Edwards eight.

Going into the primary, Clinton had 218 delegates, Obama had 127 and Edwards had 53, according to delegate counts done by CNN and The Green Papers, a nonpartisan Web site that compiles election statistics. That includes endorsements from so-called superdelegates, Democratic officeholders and party officials, who aren't bound by primary and caucus results.

A Democrat needs 2,025 of 4,049 delegates to win the nomination.

To contact the reporters on this story: Kristin Jensen in Washington at kjensen@bloomberg.net; James Rowley in Washington at jarowley@bloomberg.net

Last Updated: January 26, 2008 23:04 EST