WRAPUP 12-Democrat Obama rolls to three big U.S. wins

(Updates with Obama, McCain speeches)

By John Whitesides, Political Correspondent

WASHINGTON, Feb 12 (Reuters) - Barack Obama easily won three more Democratic nominating contests on Tuesday, extending his winning streak over rival Hillary Clinton and building momentum in a hard-fought U.S. presidential race.

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.

"Tonight, we're on our way. But we know how much further we have to go," Obama told supporters in Madison, Wisconsin, where the next showdown occurs in a week. "We know our road will not be easy. But we also know that at this moment the cynics can no longer say our hope is false."

Republican front-runner John McCain also swept to wins over his last major challenger, former Arkansas Gov. Mike Huckabee, in the U.S. capital area contests as he moved closer to clinching the party's nomination for the November election.

McCain already was looking forward to a general election match-up with the Democrats after Tuesday's wins, which will increase pressure on Huckabee to give up his White House quest.

"Now my friends comes the hard part, and for America, the much bigger decision," McCain, an Arizona senator, told supporters in Alexandria, Virginia.

"We do not know for certain who will have the honor 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," he said.