INDIANAPOLIS (AP) - Barack Obama swept to victory in the North Carolina primary on Tuesday but fell behind Hillary Rodham Clinton in Indiana, the last big-delegate prizes left in their long race for the Democratic presidential nomination.

Obama's win mirrored earlier triumphs in Southern states with large black populations, Georgia, Alabama, Louisiana and South Carolina among them.

That made Indiana a virtual must-win Midwestern state for the former first lady, who was hoping to counter Obama's persistent delegate advantage with a strong run through the late primaries.

Returns from 40 percent of Indiana precincts showed Clinton with 56 percent of the vote to 44 percent for Obama.

In North Carolina, Obama was gaining 64 percent of the vote.

Exit polls indicate the economy has been on voters' minds in Democratic primaries in Indiana and North Carolina.

Two-thirds of Democratic primary voters in Indiana and nearly as many in North Carolina who were surveyed said the economy is the most important issue facing the nation. That's more than have said so in 28 previous competitive Democratic primaries with exit polls this year.

Only about one in five in each state said Iraq was the top issue, and even fewer picked health care from a list of three issues.

Exit polls in Indiana show that about half the voters say the controversy over the Rev. Jeremiah Wright was an important factor in their vote.

But preliminary data from those polls show that the focus on Wright, Barack Obama's former pastor, is not giving Hillary Rodham Clinton a big advantage. Those who said the Wright situation influenced their decision are leaning heavily toward Clinton, while those who dismiss his importance are leaning nearly as strongly toward Obama.

The exit polls also show that Clinton is continuing to do strongly with working-class white voters, a pivotal group that Obama has been struggling to win over. Two-thirds of working-class whites are backing Clinton, while blacks are overwhelmingly supporting Obama.

Indiana's Democratic primary is 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.

North Carolina and Indiana are looking like the last chance for the Democratic candidates to take in a big chunk of pledged delegates.

Altogether, 187 delegates are at stake in the two states. After today, there are just 217 pledged delegates up for grabs in the six remaining contests, including 52 from Oregon.

North Carolina and Indiana can't mathematically settle the nomination for either Barack Obama or Hillary Rodham Clinton. A candidate needs 2,025 delegates to win, and -- as of yesterday -- Obama had 1,745.5 to Clinton's 1,608.

The key to the nomination is held by superdelegates, of which about 220 are still undecided. Oregon has 13 total superdelegates.

Clinton's main hope is to persuade most of the still-neutral superdelegates to disregard his lead in the delegate chase and support her instead. She is also hoping to get delegates from Michigan and Florida seated at this summer's convention.