Obama crosses key threshold

— -- A split decision in the Oregon and Kentucky primaries Tuesday pushed Barack Obama across an important threshold, giving him a majority of elected delegates and bolstering his claim to the Democratic presidential nomination.

Hillary Rodham Clinton swept Kentucky by a 2-1 margin, vowing at a victory rally in Louisville that she would stay in the race at least through closing contests in Montana and South Dakota in two weeks.

Even so, Obama marked his Oregon victory with a rally in Des Moines, returning to the state where the opening Iowa caucuses four months ago sent his presidential bid soaring. He sought to pivot from a fierce primary fight to a general-election battle against presumptive Republican nominee John McCain.

"You came out on a cold winter's night in January in numbers that this country had never seen, and you stood for change," Obama told a crowd of more than 6,000, the state Capitol behind him. "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."

Clinton said neither she nor Obama could claim the "magic number" needed to clinch the nomination. "I'm going to keep making our case until we have a nominee, whoever she may be," she said to cheers.

Clinton defeated Obama in Kentucky by a wide margin, 65%-30%. Obama topped Clinton in Oregon. As of 12:41 a.m. ET, with 89% of precincts reporting, Obama led Clinton 58%-42%.

When the day began, Obama was 17 delegates short of a majority of elected delegates, according to the Associated Press. The allocation of 51 Kentucky delegates and 52 Oregon delegates gave him more than that.

He ended the evening needing support from about 60 more delegates to reach the 2,026 delegate count required for nomination. He has gained nearly that many endorsements from superdelegates during the past two weeks.

"There is an inexorability to Barack Obama's campaign now," says political scientist Ernest Yanarella of the University of Kentucky, "and a sense that Kentucky may be Hillary's last hurrah."