Barack Obama has easily won three more Democratic nominating contests, extending his winning streak over Hillary Clinton and building momentum in a hard-fought US presidential race.
Mr Obama rolled to decisive victories in Virginia, Maryland and the District of Columbia, running his hot streak to eight consecutive wins and expanding his lead in pledged convention delegates who select the party's nominee.
US Democratic presidential candidate Senator Barack Obama addresses supporters last night
Republican front-runner John McCain also swept to wins over his last major challenger, former Arkansas Governor Mike Huckabee, in the US capital area contests as he moved closer to clinching the party's nomination for the November election.
Mr McCain already was looking forward to a general election match-up with the Democrats after last night's wins, which will increase pressure on Mr Huckabee to give up his White House quest.
"Now my friends comes the hard part, and for America, the much bigger decision," Mr McCain, an Arizona senator, told supporters in Alexandria, Virginia. "We do not know for certain who will have the honour of being the Democratic Party's nominee for president. But we know where either of their candidates will lead this country, and we dare not let them."
The wins for Mr Obama followed big weekend triumphs in Maine, Louisiana, Nebraska, Washington and the Virgin Islands.
All three of yesterday's contests occurred in fertile territory for Mr Obama, with large populations of the highly educated, high-income and black voters who have favoured the Illinois senator.
But exit polls indicated Mr Obama dramatically expanded his support and cut into Mrs Clinton's core groups. Mr Obama led among women, Hispanics and lower-income voters in Virginia and essentially split the votes of whites with Mrs Clinton. In Maryland, he captured seniors and rural voters.
"This is the new American majority," Mr Obama said. "This is what change looks like when it happens from the bottom up."
Mr Obama already had edged past Mrs Clinton in the race for pledged delegates who formally select a party nominee at a convention in August. A total of 168 Democratic delegates were at stake in yesterday's voting.
Mr Obama had 1,017 pledged delegates to Mrs Clinton's 942, according to a count by MSNBC - well short of the 2,025 needed to clinch the Democratic nomination.
Among Republicans, Mr McCain has built a nearly insurmountable lead in delegates to the party's nominating convention and became the likely nominee last week with the withdrawal of top rival former Massachusetts Governor Mitt Romney.
Mr McCain had won 785 of the 1,191 delegates needed for nomination - an overwhelming lead on Mr Huckabee, who had 240.
But Mr Huckabee won two of three contests on Saturday as Mr McCain, an Arizona senator, struggled to win over disgruntled conservatives unhappy with his record on immigration, taxes and other issues.