Many of her supporters say he's inexperienced, slick and nothing more than a great motivational speaker. Many of his supporters are so solidly behind him they can't even bring themselves to think about voting for her.
By now it's clear that the race for the Democratic nomination won't be over any time soon. But the contest is not just about Hillary Rodham Clinton or Barack Obama. It has become about black vs. white, young vs. old, men vs. women and one base of staunch supporters vs. another.
Despite the overtures these two historic candidates have made toward each other in recent debates and even last week on the Senate floor, there are indications that the increasingly negative tone between their campaigns -- whether over national security and NAFTA or comments related to race or gender -- is being mirrored on the ground level as supporters on both sides question their willingness to back the other candidate should their preference fail to win the nomination.
When Clinton met last week in Washington with the Black Press of America, a group representing some 200 black community newspapers across the country, she tried to explain her recent hints about a possible joint ticket. "I think that every day someone says to me, 'I can't make up my mind between the two of you -- I am so torn,' and I hear that all the time across the country," she said.
While it may be true that some voters are torn between the two, it appears that many more are not. Polls have pointed out what could become a huge headache for Democrats in the general election. An NBC News/Wall Street Journal survey released last week showed that a third of Obama voters have a low opinion of Clinton and a fifth of Clinton backers have a low opinion of Obama. (Clinton's favorable/unfavorable rating among her rivals' supporters was 45 percent to 33 percent, while Obama's rating among Clinton fans was 55 percent to 20 percent.) A recent Pew Research Center poll reached similar conclusions.
"Right now, we are in the heat of battle. There are a bunch of my supporters who I am sure are frustrated with her and her campaign and some of the tactics she has been employing," Obama said when asked about the Pew poll. "But, you know, the truth is that when you have a convention and the nominee is there and it becomes clear that this is a contest for the issues that we as Democrats care deeply about, I'm very confident that we'll be able to rally the country together."
That may be wishful thinking. More than two dozen interviews with supporters of both candidates in Texas, Mississippi, Pennsylvania, Wyoming and Ohio painted a more troubling picture for the future nominee, no matter who it is.
For all the history-making enthusiasm both candidates have brought to the race, someone has to win, and while several Clinton backers, particularly union workers, said they would support Obama in the general if they had to, about half said they didn't know what they would do or whether they would support John McCain. Nearly all of them were concerned that Obama was too inexperienced to be commander in chief.
"I think he's a great motivational speaker, but what I hear from him I could go hear at my church on Sunday from my pastor, and to me he just seems all fluff," said 40-year-old Maria Aguirre on the morning of the Texas "primacaucus." "If [Clinton] doesn't manage to win the nomination, then I will vote for McCain, because he's got experience and if someone has to answer the phone at 3 o'clock in the morning and if it can't be her, I'd rather it be McCain."
A college administrator standing on the sidelines of a rally at Temple University last week complained that she hadn't been able to "connect" with Obama in part because his speeches lacked specifics. A young law student from Cotulla, Texas, suggested Obama fans were being had and said she'd have a hard time supporting him.
"If Barack Obama wins, I'll have to wait. I've told people, I have to do a lot of self-cleansing, meditation and yoga," said Vanessa Russell-Evans, 26. "As a woman and as somebody who's wanted Hillary to run since I was 10 when she became the first lady, it's almost like it's being taken away... [by] someone who is saying a lot of poetry, a lot of fluff, a lot of stuff that I feel that, you know... [George W.] Bush did that eight years ago. He ran on a campaign that was compassionate conservatism. It was this wave of coolness, and I feel that Obama's campaign is like that, too. It's this wave of coolness; everybody's sort of being sucked in. I mean, the rallies are sort of like revivals.... People are fainting."
For their part, hard-core Obama fans -- described at times by rivals and fellow supporters alike as obsessed, enamored or infatuated -- just could not bring themselves to imagine Obama losing the nomination, especially since he is leading in both pledged delegates and in the popular vote. And they didn't do much to hide their qualms with Clinton, even as some begrudgingly said they'll back her if necessary.
"Personally, I would like to see Mrs. Hillary Clinton drop out as soon as possible and get Barack the nomination," said John Harris, from Walton, Miss., who formed an Obama supporter group through the candidate's Web site and holds fundraisers for him. Still, Walton said he'll vote for whoever wins the Democratic nod.
At an Obama rally in Jackson, Miss., on March 10, the largely black crowd booed four separate times at the mention of the former first lady. In Ohio, the Illinois senator made a point of asking the mostly white crowd to stop booing her.
It's clear that there are strong feelings on both sides, and the issues of race and gender have further complicated things. There appears to be a black-white divide among Obama backers when it comes to expressing support for Clinton if she gets the nomination. In interviews, white Democrats were far more willing to say they would support her if she becomes the Democratic nominee -- even if they doubted her ability to defeat McCain -- while black voters were more likely to hedge.
Take Emma Sanders, from Jackson, Miss., who said, "I hate to think about that. I feel that Obama is going to win and that he'd be the nominee of the Democratic Party.... I don't think I'm going to have to vote for her. That's a long ways off. I would have to make up my mind at that point."
Among Clinton supporters interviewed, white women were the most likely to say they would have to seriously consider whether to vote for Obama. In fact, the Pew poll showed that some 20 percent of white Democrats said they would vote for McCain if Obama is the Democratic nominee, which is twice the percentage of white Democrats who said they would support the Arizona senator in a Clinton-McCain matchup.
When it comes to deciding the winner of this fight, Obama supporters were more willing to redo the Florida and Michigan primaries, while Clinton supporters were more likely to argue that those results should stand and that superdelegates should choose the nominee they believe would be best for the party's prospects in November. Voters on both sides expressed a desire for the issue to be worked out before the convention.
"The more fighting involved in the ticket, the worse it looks and the better it makes the Republicans look," said Denise Decker, a 50-year-old church secretary from Old Forge, Pa.
Senate candidate Nick Carter, a Democrat from Laramie, Wyo., worried that the longer the race continued, the stronger the bad feelings would be among voters whose candidate is not "the chosen one."
"As the campaign has gone on, the Democratic Party has gotten a little more hard-edged and separated," Carter said.
At the meeting with black newspapers last week in Washington, Clinton said she was certain the party would unite for the general election and that she would expect her supporters to rally around Obama if he's the nominee "because the most important question is whether we're going to have a Democratic president come next January."
The Democratic Party and its supporters across the country are hoping that's the case.
NBC News/National Journal campaign reporter Aswini Anburajan contributed to this report.