Barack Obama won a healthy victory over Hillary Clinton in Oregon, and is projected to take 30 of 52 pledged delegates in the state. Clinton also won handily in Kentucky, but it didn't give her enough delegates to secure a chance of winning the nomination.
Clinton has vowed to continue the fight through the last primaries in early June _ determination which was cheered on by a group of female supporters from the WomenCount political action committee who took out a full-page ad in The New York Times urging her not to give up.
After Tuesday's primaries, Obama has 1,961 out of 2,026 needed to secure the nomination; Clinton has 1,777.
But despite an almost sure victory, former Sen. Tom Daschle, a key Obama adviser, urged Democrats to unite behind Obama, bringing the marathon primary contest to an end so that the party could focus on the November general election battle against presumptive Republican nominee John McCain.
Democrats have worried that the prolonged, and frequently combative, primary campaign will undermine the party's chances of recapturing the White House from the Republicans.
"We want to begin the process of bringing this party together, and I think that over the last few weeks we've seen indications at virtually all levels in both campaigns that there's a desire to do that," Daschle told CBS's "The Early Show" on Tuesday. "That doesn't mean we're going to do it tomorrow or the next day, but clearly there is a desire to unify."
Clinton was favored to win by a large margin in Kentucky as voters cast their ballots there, while Obama was expected to take Oregon.
The Illinois senator's campaign is touting the milestone as a big step toward ending the epic nomination battle with Clinton.
Having a majority of delegates elected in state primaries and caucuses could help Obama's case with undecided superdelegates _ the party insiders who are not tied to primary or caucus results _ to pick up the pace of their endorsements. Superdelegate support is crucial because neither candidate will have enough delegates from the remaining primaries to clinch the nomination without them.
Obama added another superdelegate to his column Tuesday, Guam congressional delegate Madeleine Bordallo. Of the nearly 800 superdelegates, about a quarter of them have not declared support for either candidate.
Including superdelegates, Obama had 1,917 delegates to Clinton's 1,721 going into Tuesday's primaries in which 103 delegates were at stake.
McCain has already been targeting Obama in his campaign speeches as his likely opponent in the November election. On Monday the longtime Arizona senator accused Obama of inexperience and reckless judgment for saying Iran does not pose the same serious threat to the United States as the Soviet Union did in its day.
Obama has been increasingly presenting himself as the nominee as he looks ahead to the battleground swing states in the general election. On Tuesday night, he planned to hold a rally in Iowa, where he won the leadoff caucuses in early January.
Of the nearly 800 superdelegates, about a quarter of them have not declared support for either candidate.
Clinton has mounting campaign debts, but she vowed there was "no way that this is going to end anytime soon" as she campaigned Monday in Kentucky.
The New York senator soldiered on through event after event, ending her night Monday in Louisville before a crowd of several hundred, her voice raspy.
"There are a lot of people who wanted to end this election before you had a chance to vote," she said, husband and former President Bill Clinton at her side. "I'm ready to go to bat for you if you'll come out and vote for me."
Obama, seeking to become the first Black U.S. president, won the endorsement of Sen. Robert Byrd of West Virginia, the longest-serving senator in history and a former member of the white supremacist Ku Klux Klan and one-time opponent of civil rights legislation.
Nationally, Obama holds his largest lead yet over Clinton in the Gallup Poll, 55 percent to her 39 percent. The poll, released Monday, was conducted among 1,261 Democratic voters and has a 3 percentage point margin of error. Back in mid-January, Clinton held a 20 percentage point lead in the Gallup Poll.
Obama campaigned Monday in Montana, where voters will join those from South Dakota on June 3 in dropping the curtain on the 2008 primary and caucus season. Clinton planned to spend primary night in Louisville, Kentucky. Obama slated a rally for Iowa, where he won the caucus in the campaign season's opening salvo, seeking to convey a sense of closure to the Democratic campaign.
The Illinois senator rarely mentions Clinton now except to praise her "magnificent" campaign. Instead, Obama has sought to exploit McCain's ties to lobbyists.
McCain recently adopted conflict-of-interest guidelines that led to the departures of several campaign aides due to their links to lobbyists. After Tuesday, only three primaries remain on the Democratic calendar. Puerto Rico, with 55 delegates, holds its primary on June 1; Montana, with 16 delegates, and South Dakota, with 15, vote two days later.