Meanwhile, last week Obama disavowed his pastor of 20 years, Rev. Jeremiah Wright, who in a series of public appearances reiterated some of his most controversial statements, including that the United States had created the virus that caused AIDS, that American foreign policies invited the 9/11 attacks, and other incendiary comments.
Exit poll results indicate that just under half of Democratic primary voters in Indiana and North Carolina alike call the controversy surrounding the Rev. Jeremiah Wright an important factor in their vote.
In both states around three-quarters of voters or more say they made up their minds before last week, according to preliminary exit polls, when the controversy over Wright's comments reignited.
In recent days Clinton has tried to re-set the bar for winning the Democratic nomination. Asked what she sees the finish line of the race as, she said for the first time: "I think it's 2209."
That figure — 2209 delegates — assumes that Florida and Michigan's delegates are included in the overall count. However, Democratic Party officials have long said the magic number for winning the nomination was 2025, a number that does not include Florida and Michigan, states that did not hold candidate-supported primaries after a bitter dispute with the national party over the primary calendar.
"There are going to be the rest of these contests which are very significant and then in June if we haven't done it already were going to have to resolve Florida and Michigan. And they were legitimate elections," Clinton said Tuesday.
Clinton Communications Director Howard Wolfson confirmed Clinton will meet with undecided superdelegates Wednesday to "ask for their support."
While voters continue to appear energized, many in the Democratic party worry the ongoing nomination battle will hurt the party going into the general election.
"We're beyond the point of this being good for the party," Carrick said. "We're getting to the point where it's just snarky, back-and-forth, gotcha stuff that's doing damage to the party."
Exit poll results indicate a continued criticism of Clinton for the tone of the campaign.
In North Carolina two-thirds of voters said she attacked her opponent unfairly, as did about six in 10 in Indiana, reports ABC News' Gary Langer.
Fewer in both states -- closer to four in 10 -- said Obama attacked unfairly.
Before the primaries in North Carolina and Indiana, both candidates suggested the Democratic battle could go until the last primaries in Montana and South Dakota on June 3, and even until the party convention in Denver this August, where superdelegates could ultimately decide the Democratic nominee.
"These two candidates are prepared to go to the bitter end," predicted Donna Brazile, who ran Al Gore's 2000 presidential campaign and is an ABC News contributor.
"They're committed. They have staff, they have offices, they have telephones, they have volunteers signed up," she said. "Some of them have already visited Oregon and Montana, so let's assume it's going until the bitter end."
But after her disappointing finishes Tuesday night, and with Clinton almost out of political maneuvers, her quest to become the nation's first woman president appears increasingly unlikely.