Hillary Rodham Clinton is the winner of the Democratic presidential primary in Indiana, while Barack Obama swept to victory in the North Carolina race.

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With about 99 percent of the precincts reporting, Clinton leads Obama 51 percent to 49 percent, a margin of little more than 22,000 votes out of more than 1.2 million cast, The Associated Press said in its projection.

The outcome wasn't clear for more than six hours after the polls closed, the uncertainty stemming from slow counting in Lake County near Obama's home city of Chicago.

Earlier in the evening, Clinton sounded optimistic about her chances when she addressed supporters in Indianapolis, commending them for "your victory."

"Thanks to you, it's full speed to the White House," she said, signaling her determination to fight on in a campaign already waged across more than 15 months and nearly all 50 states.

Obama savored his North Carolina victory during a speech in Raleigh.

"Tonight we stand less than 200 delegates away from securing the Democratic nomination for president of the United States," Obama said.

"This has been one of the longest, most closely fought contests in history. And that’s partly because we have such a formidable opponent in Sen. Hillary Clinton," Obama said. "Yes, there have been bruised feelings on both sides. Yes, each side desperately wants their candidate to win. But ultimately, this race is not about Hillary Clinton or Barack Obama or John McCain. This election is about you, the American people, and whether we will have a president and a party that can lead us toward a brighter future."

But he also took aim at McCain.

"We all agree that at this defining moment in history -- a moment when we're facing two wars, an economy in turmoil, a planet in peril -- we can't afford to give John McCain the chance to serve out George Bush's third term."

Clinton also struck a tone of unity, while drawing attention to the history-making Democratic campaign which, for the first time, pits a black man against a white woman.

"I want to commend Sen. Obama and his supporters on their win in North Carolina. We are, in many ways, on the same journey," she said. "It’s a journey begun long before we were born. It is a journey by men and women who have been on a mission to perfect our union, who marched and protested, who risked everything they had to build an America that embraces us all."

Next up for the Democratic rivals is West Virginia on May 13. A Rasmussen poll taken Monday has Clinton leading 56 to 27 percent over Obama, with 17 percent undecided. West Virginia has 39 delegates up for grabs and should be favorable ground for Clinton because of her success appealing to blue-collar voters who are prevalent in the state.

On Tuesday, race again played a pivotal role, as whites in Indiana and North Carolina leaned solidly toward Clinton and blacks voted overwhelmingly for Obama, exit polls showed. Half the voters said they were influenced by the focus on Obama's former pastor, the Rev. Jeremiah Wright.

Obama again failed to make an appreciable dent in a crucial voting bloc that has consistently eluded him -- working-class whites.

According to preliminary results from the exit polls, two-thirds of whites in both states who have not completed college were supporting Clinton, which the New York senator could use to fortify her argument that she would be the stronger Democratic candidate in the November general election. Of 28 states that have held primaries in which she and Obama competed before Tuesday, Clinton had prevailed with working-class white voters in 25.

Wright was a looming factor in the voting, with half in each state saying he was important in choosing a candidate. Of that group, seven in 10 in Indiana and six in 10 in North Carolina backed Clinton. Those discounting him as a factor heavily favored Obama. In North Carolina, Obama got more votes from people saying they discounted the Wright episode than Clinton got from those affected by it.

Both races were dominated in the final days by Clinton's call for a summertime suspension of the federal gasoline tax, which Obama ridiculed as a stunt that would cost jobs.

Indiana's Democratic primary was open to all voters. About one in five said they were independents and one in 10 identified themselves as Republican. North Carolina's Democratic primary was open only to voters registered Democratic or unaffiliated; nearly one in five voters in that contest called themselves independents.

The exit poll estimated blacks made up about a third of voters in the North Carolina Democratic primary, about one in seven in Indiana. More than half of voters in both states were women, which is typical for Democratic primaries. About one in seven voters in Indiana and slightly fewer in North Carolina were under age 30; about a quarter in North Carolina and somewhat fewer in Indiana were over age 65.