Hillary Clinton won the Kentucky Democratic primary by a wide margin on Tuesday, while Barack Obama appeared to be heading for a comfortable victory in Oregon.
By Andrew Ward in Washington
With over 90 per cent of the vote counted in Kentucky, Mrs Clinton was leading her rival by 65 per cent to 30 per cent.
She told supporters at a victory rally she had no intention of retiring from the race. ”I’m going to keep making our case until we have a nominee – whoever she may be,” she insisted.
Mr Obama is almost certain to finish the night with a majority of the delegates available from the state-by-state nominating contests, bringing him a step closer to becoming the Democratic presidential nominee.
But the Illinois senator was expected to stop short of declaring outright victory over Mrs Clinton.
News organisations declared Mrs Clinton the winner in Kentucky immediately after voting finished, based on early results and exit polls that showed her with a lead of up to 30 percentage points.
Results from Oregon were not due until later on Tuesday but recent opinion polls have shown Mr Obama with a 10-point advantage.
Mr Obama needed to win just 15 of the 103 delegates up for grabs in Kentucky and Oregon to gain a majority of the 3,253 available nationwide.
Tom Daschle, co-chairman of the Obama campaign, said Mr Obama was poised to pass a “critical milestone” but said the race was not yet over.
Mr Obama has also taken the lead among the nearly 800 Democratic officials, known as “superdelegates”, whose votes look likely to decide the contest in his favour. Before Tuesday night’s results, Mr Obama was a little more than 100 short of the 2,026 delegates needed to clinch the nomination.
Mrs Clinton’s victory in Kentucky highlighted her strength among the white, working class voters who dominate that state and reinforced doubts about Mr Obama’s ability to win support among that group in the general election.
Kentucky is similar in nature to neighbouring West Virginia, where Mrs Clinton last week won the state Democratic primary by 40 percentage points.
Two thirds of Clinton supporters in Kentucky told exit pollsters they would not vote for Mr Obama in November, with 41 per cent prepared to support John McCain, the Republican presidential candidate, while 23 per cent would stay at home.
Kentucky is one of the more conservative states in the US, with only a third of voters describing themselves as liberal. Oregon, in contrast, is among the most liberal, with almost six in 10 voters identifying with that label.
Both of Tuesday’s contests were so-called “closed primaries” open only to registered Democrats. The remaining primaries take place in Puerto Rico on June 1 and South Dakota and Montana two days later.