By winning critical contested strongholds in Massachusetts, New Jersey and — most important — California, Sen. Hillary Rodham Clinton of New York showed big-state muscle and remained the putative leader. Decisive red-state victories in Oklahoma and Tennessee bolstered her assertions of electability.
But Sen. Barack Obama of Illinois proved the breadth of his national appeal and national organization in winning six more primaries and caucuses than his rival.
He narrowly beat Clinton in the key interior state of Missouri. He didn't clearly reverse the campaign narrative or seize the momentum of the race, but he ground out a rough tie in the number of delegates each campaign accrued.
"I look forward to continuing our campaign and our debate about how to leave this country better off for the next generation,” Clinton said, declaring victory before the confetti fell in a New York ballroom.
Obama's aides argued that he is the one with a clearer path to victory. He raised more than twice as much money as Clinton in January, bringing it in at a pace of about $1 million a day. And the next seven contests seem to favor him: Four are in states (including the District of Columbia) with heavy African-American populations, and three are caucuses, structures which have favored Obama to this point.
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"This was their day to get the upper hand in the nomination fight, and they most decidedly failed in that regard," Obama campaign manager David Plouffe told reporters in Chicago.
Super Tuesday revealed the candidates' strengths as well as their weaknesses. Obama has built a stunning bulwark among African-American voters, who gave him 82 percent of their votes in New Jersey, 87 percent in Georgia and 84 percent in New Jersey, according to exit polls.
He proved that his victory in lily-white Iowa was no fluke, picking up victories in whiter-still Idaho and nearly-as-white Utah. And he beat Clinton among white voters in California.
But Clinton maintained her strength among women in the big states. And she won by large margins among Hispanic voters around the country and among Asian voters in California, where those two minorities provided her with a margin of victory that overwhelmed the more widely noted African-American vote.
The two candidates spoke to their respective supporters late Wednesday, each making a case for his or her electability against the likely Republican nominee, Sen. John McCain of Arizona.
"Our time has come, our movement is real, and change is coming to America," Obama said.
Then he turned to probing one of his rival’s main weaknesses: the perception that Clinton is divisive.
"It's a choice between going into this election with Republicans and independents already united against us and going against their nominee with a campaign that has united Americans of all parties, of all backgrounds, of all races, of all religions, [for] a common purpose," he said to a crowd that chanted, at times, "USA, USA."
Clinton mirrored that attack approach, seeming to refer to Obama's vulnerability to as-yet-unknown GOP assaults.
“I won't let anyone swift-boat this country's future," she said.
Clinton also shifted her rhetoric in a speech that senior adviser Ann Lewis said had been crafted by a different team than earlier in the race, one that included Maggie Williams, a former White House aide who recently joined the campaign.
"She wanted something different, and she got it," Lewis said of Clinton's speech.
The speech was notably more rhythmic and florid than in earlier addresses. Clinton pledged to workfor "people on the day shift, the night shift, the late shift with the crying baby" and for "all those who aren't in the headlines but have always written America's story."
The final flourish echoed a signature line of Obama, who promises "a nation healed, a world repaired."
"Give us this nation to heal, this world to lead, this moment to seize," Clinton said. "I know we're ready."
Clinton benefited from a late batch of polls news reports overstating Obama's gains, and from early exit polling that suggested he might win New Jersey and Massachusetts — figments that nevertheless had television commentators framing her as something of an upset victor.
And her win in Massachusetts demonstrated the limits of three much-touted Obama endorsements: The state's senior senator, Edward M. Kennedy; its junior senator and the 2004 Democratic presidential nominee, John F. Kerry; and its governor, Deval Patrick.
Election results indicated a slim margin of delegates separated the two Democratic candidates, and most estimates give Obama a lead among delegates awarded in the primaries and caucuses.
Clinton, however, holds an overall lead because of her support from "superdelegates" — Democratic officials who choose where to throw their support. And her campaign has begun to lobby for the inclusion of a delegation from Florida, a state she won in a vote that isn't recognized by the Democratic National Committee.
Now, the campaigns will continue the fight for delegates, and for the campaign's uncertain narrative that at the moment pits a resilient front-runner against a challenger's momentum.