Hillary Clinton captured the first of two Democratic nominating tests on Tuesday with a big win in Kentucky, but front-runner Barack Obama claimed a major milestone that put him within reach of his party's presidential nomination.
Clinton crushed Obama by 35 points in Kentucky, where she again performed well with white working-class voters who have been her biggest supporters. But the results, and later returns in Oregon, gave Obama a majority of pledged delegates won in the lengthy state-by-state nominating fight with Clinton.
Obama hoped that milestone marked the beginning of the end of their gruelling Democratic race for the right to face Republican John McCain in November's election.
"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," Obama told supporters in Iowa, site of his breakthrough win in the first Democratic contest on January 3.
At a rally outside the Iowa state capital building in Des Moines, the Illinois senator turned his attention to a showdown with McCain and said their November battle would represent "more of the same versus change. It is the past versus the future."
But Clinton gave no sign of surrender, promising supporters in Kentucky that she would keep fighting until the Democratic voting ends on June 3.
"I'm going to keep making our case until we have a nominee -- whoever she may be," Clinton, who has shrugged off calls to drop out of the race for weeks, told supporters in Louisville.
"We have to select a nominee who is best positioned to win in November and someone who is best prepared to address the enormous challenges in these difficult times," the New York senator and former first lady said.
Even with Tuesday's results, Obama will still be about 50 delegates short of the 2,026 needed to win the nomination at the Democratic convention in August. But he hopes the milestone will start more undecided superdelegates -- party officials who can back any candidate -- flooding his way.
He contends those superdelegates, who have been breaking his way heavily in recent weeks, should support him because he won the most delegates in state voting.
Clinton says they should reconsider because she would be a stronger opponent for McCain, an Arizona senator. Her victories in big states like Pennsylvania and Ohio gave her a broader base of support than Obama, she said.
"Neither Senator Obama or I will have reached that magic number when the voting ends June 3," Clinton said in Louisville of the number of delegates needed to win the nomination. "So our party will have a tough choice to make."
Exit polls showed Obama, who would be the first black U.S. president, again had difficulty with white working-class voters in Kentucky. Clinton won more than 70 per cent of white voters, and three-quarters of those who did not finish college.
About 20 per cent said race played a factor in their vote -- similar to the percentage last week in West Virginia, where Clinton trounced Obama.
Oregon's balloting ends at 8 p.m. PDT/11 p.m. EDT (4 a.m. British time on Wednesday) Results are expected shortly after.
A delegate count by MSNBC gives Obama 1,931 delegates to Clinton's 1,725. After Tuesday, only three contests remain, with 86 delegates at stake.
Obama's success has been fuelled by record fundraising. He reported raising $31.3 million (15.9 million pounds) in April, down from the $42.8 million he raised in March, and had $37.3 million in the bank to fund his campaign, his campaign said.
Tuesday was the deadline for filing monthly financial reports with the Federal Election Commission. Clinton spokesman Howard Wolfson told CNN she raised $22 million in April, up slightly from $20.9 million in March.
He did not say how much the campaign, which has admitted to being more than $20 million in debt, had on hand or still owed creditors.
(Additional reporting by Jeff Mason and Ellen Wulfhorst; Editing by Doina Chiacu)