In Indiana, where the race was too close to call, MSNBC showed Clinton, the senator from New York, leading Obama, the senator from Illinois, 51 percent to 49 percent with 91 percent of the vote counted. Only about 21,000 votes separated the two candidates.

Lake County, where Gary is located, was reported slow tallying its votes.

Obama had been widely expected to beat rival Clinton in the Tar Heel State. With 98 percent of the vote counted, Obama had done just that, leading 57 percent to 43 percent, CNN said.

Turnout in the North Carolina primary was expected to reach 50 percent, Gary Bartlett, executive director for the state Board of Elections, told CNN. Fifteen to 30 percent is normal for a primary, he said.

In Indiana, a secretary of state's office spokeswoman said voter turnout was high, as well.

Both campaigns and political observers say Tuesday's results could shift the election. If Clinton splits she can boast of momentum and being the candidate who can take the must-win states. If Obama wins both, pundits say Clinton's run is finished.

"That would signal the end of the Clinton campaign," Jerry Meek, the North Carolina Democratic Party chairman who hasn't endorsed anyone in the race, told the Times. "I don't see how she could continue."

After Tuesday's primaries, six more Democratic primaries and caucuses remain. The Democratic nominating convention is in late August in Denver.

In all, 187 delegates are at stake -- 115 in North Carolina and 72 in Indiana. Obama led in the national delegate count.