Obama's big win in Oregon, combined with a share of Kentucky delegates, left him fewer than 100 shy of the 2,026 delegates needed to clinch the party's presidential nomination.
But Obama -- vying to become the first African American to head a major-party ticket -- staked no claim to the nomination, and Clinton showed no sign of standing down.
Instead, Obama celebrated the delegate milestone -- important both psychologically and mathematically -- with a Tuesday-night stop in Iowa, traveling full circle to the state where his candidacy took off with a win in the caucuses that began the nominating fight.
Standing in front of the gold-domed state Capitol, which glowed in the darkness, Obama declared: "Tonight, in the fullness of spring, with the help of those who stood up from Portland to Louisville, we have returned to Iowa with a majority of delegates elected by the American people, and you have put us within reach of the Democratic nomination for president of the United States."
He offered a salute to Clinton -- "one of the most formidable candidates to ever run for this office" -- and urged Democrats to unify once the contentious nominating season had ended. "While our primary has been long and hard-fought," Obama said, "the hardest and most important part of our journey still lies ahead."
Clinton, appearing before cheering supporters in Louisville, Ky., reiterated her intention to keep running at least until the final primaries were held June 3. Describing the contest as "one of the closest races for a party's nomination in modern history," Clinton said she was "more determined than ever to see that every vote is cast and every ballot counted."
But the New York senator commended Obama and called for a cessation of hostilities after the nomination is settled. "While we continue to go toe-to-toe for this nation, we do see eye-to-eye when it comes to uniting our party when it comes to electing a Democratic president," Clinton said.
She defeated Obama 65% to 30% in Kentucky. Obama was leading 58% to 42% in Oregon, with about three-quarters of the returns counted.
Each state was suited to the candidates' respective strengths. Kentucky is heavily rural, white and filled with the kind of working-class Democrats who have strongly favored Clinton throughout the nominating fight. Oregon is home to large numbers of independent-minded, highly educated and more-affluent Democrats, the sort who have embraced Obama in large numbers. Tuesday's voter surveys showed that pattern repeating itself.
But the vote totals and demographics were less significant than the delegate math, which gave Obama 1,956 delegates to Clinton's 1,776 in incomplete returns, according to the Associated Press. Obama was creeping close to the 2,026 needed at the Democrats' August convention in Denver. The party has two kinds of delegates: pledged, who are awarded proportionately through primaries and caucuses, and so-called superdelegates, who are free to support whomever they choose.
Increasingly, these last primaries seem like an afterthought as Obama turns his focus to the general election against Republican Sen. John McCain of Arizona. The two spent the last week sparring long-distance over foreign policy, Social Security and the influence of Washington special interests.
At the same time, the Democratic Party began to coalesce around the Illinois senator. A day after Clinton won West Virginia in a 41-percentage-point landslide, Obama picked up the endorsement of erstwhile rival John Edwards as well as the abortion-rights group NARAL Pro-Choice America.
For her part, Clinton has scaled back her criticisms of Obama on the stump and pulled the plug on TV ads criticizing her rival. But that does not mean surrender. Today, she plans to campaign in Florida, a trip she scheduled after Obama announced his intention to spend the next three days in the Sunshine State.
The trip is driven by a simple calculation: Clinton's faint hopes of winning the nomination largely depends on seating the delegates from Florida and Michigan. Clinton won the popular vote in both states, though neither seriously competed and Obama removed his name from the Michigan ballot. The Democrats' Rules and Bylaws Committee will meet May 31 to discuss whether to seat delegates from the two states, which broke party rules by scheduling their primaries too early.
The Clinton campaign hopes to shave Obama's lead to fewer than 100 delegates by June 3, at which point she would argue to superdelegates -- members of Congress and other party insiders -- that she would be the stronger general election candidate. There are about 175 uncommitted superdelegates remaining, though any of the 800 or so could switch sides at any time.
One Clinton aide, granted anonymity because he is not authorized to speak for the campaign, said: "I don't want to sound naive or foolish, but if she's willing to play this out for two weeks to see where she gets . . . then those of us who believe she'd be a better candidate in the fall don't want to give up too soon."
Three contests remain: Puerto Rico on June 1 and Montana and South Dakota on June 3. Together, they offer 86 pledged delegates.
Barabak reported from San Francisco and Riccardi from Des Moines. Times staff writers Scott Martelle and Peter Nicholas contributed to this report.
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Delegates needed for nomination, 2,026. Totals as of Tuesday:
Total delegates ...1,956
Hillary Rodham Clinton
Total delegates ...1,776
Source: Associated Press