He won the support of many white men, a group that had voted for John Edwards of North Carolina before Mr. Edwards dropped out of the race last week. Mr. Obama seems to have cut the long-established ties between black voters and the Clintons. He made slight inroads among Hispanic voters, a solid part of Senator Hillary Rodham Clinton’s base.
But one of the most intriguing finding in the surveys of voters leaving the polls across the nation on Tuesday was when they arrived at their final decision. Throughout a week when Mr. Obama was campaigning with members of the Kennedy family, when there was a sense that he was creating a movement that cut across racial and generational lines, there was a steady movement of Democrats toward Mr. Obama, the survey suggested. But those who reported making their decision on the last day bucked the trend, tending to vote for Mrs. Clinton, of New York.
Mr. Obama more than held his own against Mrs. Clinton: he won more states and may well have won more delegates, once all of them, including those from caucus states, are officially allocated.
But once again — as in New Hampshire — the result on Tuesday did not match the fervor that had been signaled by Mr. Obama’s dramatic march of rallies across the nation leading up to the vote. In that dynamic rests one of the central questions about the Obama candidacy, which may well go the heart of whether he can win the presidency. Is this campaign a series of surges of enthusiasm, often powered by the younger voters who form long lines waiting to hear Mr. Obama speak, that set expectations that are not met at the voting booth?
Or is it rather a slow-building force, one that despite faltering in New Hampshire and falling short on Tuesday in big states like California has allowed Mr. Obama to battle one of the most formidable political dynasties to a draw and will eventually propel him to victory?
The differing views of the Obama campaign’s trajectory are only one way in which this race has cleaved the party neatly in two: the Clinton Democrats and the Obama Democrats. Age, race and gender have become the dividing lines; nothing comes close to mattering as much.
The Obama Democratic Party is made up of younger voters (under 44), blacks, white men (to a more limited extent) and independents whose show of support accounted for his victories in states like Missouri. Their level of enthusiasm for Mr. Obama — their excitement about the possibility of an Obama White House — is palpable in their response to him, or in any conversation.
The Clinton Democratic Party is the party of women, older voters, Hispanics and also some white men. A Clinton rally may not have the energy of a rock concert the way an Obama rally does. Yet the older women who have embraced Mrs. Clinton as the culmination of years of hope and other core supporters are no less passionate in their intensity and devotion.
If there is a difference between these two parties, it is that Clinton Democratic voters tend to have a history of being more likely to vote, particularly compared with younger voters and, as was the case this week, black voters. That in part might account for the enthusiasm fall-off between the campaign trail and the voting booth that Mr. Obama has to deal with.
“There’s no question that he has tapped into something,” said Senator Edward M. Kennedy, the Massachusetts Democrat whose endorsement and appearances with Mr. Obama added to the Obama frenzy. “I don’t think there’s any question that it’s a phenomenon and it is broadening. But I’m mindful that crowds don’t always turn into votes.”
“These campaigns go through different transitions,” Mr. Kennedy said. “He has a very engaging kind of charm, and that is going to become stronger and stronger as he gets known.”
For all the passion Mr. Obama may be generating on the trail, Mrs. Clinton still has a bulwark in women at the polls. Mr. Obama tried to chip away at it — dispatching Oprah Winfrey and Caroline Kennedy to campaign for him, broadcasting television advertisements with women backing him — but to little if any avail.
“He had a really fantastic week last week. It’s hard to think of a candidate having a better news media week than he had,” said Geoff Garin, a Democratic pollster who is not working for any candidate. “And her support among white women was really quite durable in the face of all that.”
“Unless one of them figure out how to transcend their demographic niches, we are going to be locked into this for a long time,” Mr. Garin said. “The thing is, if you have to pick a niche in the Democratic Party, women is a pretty good niche to have.”
There are other considerations having to do with the reach of Mr. Obama’s appeal that are going to come increasingly into play in a contest in which Mr. Obama and Mrs. Clinton seem to be arm-wrestling for each delegate.
Mr. Obama split the white male vote nationally with Mrs. Clinton, but there was an important geographical disparity there: White men in California voted for Mr. Obama but white men in Southern states like Alabama did not. The question is what white men in Ohio will do next month, during what is shaping up as a critical showdown for Mr. Obama and Mrs. Clinton.
Mr. Obama showed signs of doing slightly better with Hispanic voters in some states than he did in Nevada earlier this month, and Mr. Kennedy suggested this augured well for the Texas primary next month, with its heavy population of Latino voters. Still, if Mr. Obama is making progress with these voters, Mrs. Clinton still has the upper hand.
But at the end of the day, the task for Mr. Obama may well transcend the demographics or voting blocs that are the brick and mortar of the traditional American campaign. As even Mrs. Clinton’s aides will acknowledge, Mr. Obama has brought a level of excitement and involvement to the campaign trail that few people involved in this contest have seen before. The question is whether he can move them one more step on the electoral process — into voting — in the dwindling number of contests that make up this campaign.