In Indiana, Obama won among self-described independents, a group that has favored him throughout the campaign, but narrowly lost that vote to Clinton in North Carolina.
Clinton won white voters over 45 by wide margins in both Indiana and North Carolina, as she has in other states, though Obama narrowed her advantage among those voters, exit polls showed, and outperformed her among under-30 whites.
Voter turnout set records in both states, which had not held meaningful Democratic presidential primaries in decades.
Amid high gasoline prices and Clinton's hotly debated proposal for a gas-tax holiday, the economy was cited by roughly two in every three of primary voters as the most important issue, the highest proportion of the '08 campaign. The war in Iraq was the top concern for only one voter in five.
With six primaries remaining, Clinton could well collect more delegates than Obama in the final contests. She is favored in West Virginia next week, Kentucky on May 20 and Puerto Rico on June 1.
But the relatively small number of delegates at stake and party rules that award almost as many delegates to the runner-up mean she has no chance of overtaking Obama in pledged delegates by the time the primaries end.
Obama's camp projects that he will gain a majority of the pledged delegates when Oregon votes May 20, a contest he is expected to win.
Neither candidate can secure the nomination with pledged delegates alone, putting the power to choose a nominee in the hands of about 800 superdelegates, elected and party officials who are free to vote for either candidate.
Some 220 superdelegates remain undeclared, and Clinton would need considerably more of them than Obama in order to prevail, according to current projections. The Obama campaign estimates that she would need to win 70 percent of the remaining superdelegates to become the nominee.
Clinton's campaign is hoping that party leaders will help her close the pledged delegate gap by resolving a long-running dispute over awarding delegates from Florida and Michigan, whose primaries did not count toward the nomination because they were held in violation of party rules. On May 31, the Rules and Bylaws Committee of the Democratic National Committee will meet in an effort to resolve the impasse.
A plan the panel is considering would award half of Michigan and Florida's delegates on the basis of the primary vote, giving Clinton about 55 more delegates than Obama. That would still not be enough for her to overtake him in pledged delegates.
With neither state included, it would take 2,025 to clinch the nomination. Going into this week's primaries, Obama had 1,745.5 delegates, to 1,608 for Clinton, according to the Associated Press.
paul.west@baltsun.com
