Democrat Barack Obama and Republican John McCain were the big winners Tuesday in presidential primaries in Maryland, Virginia, and the District of Columbia. VOA National Correspondent Jim Malone has the latest on the U.S. presidential race from Washington.

Barack Obama is on a roll.

"We have now won east and west and north and south and across the heartland of this country we love," he said.

Obama won all three primaries by a comfortable margin. He won about 90 percent of the African-American vote in all three contests and broadened his base of support among white voters, including both men and women.

Eager to look ahead, Hillary Clinton is already campaigning in Texas, which holds its primary on March 4.

"I am tested. I am ready," she said. "Let us make it happen!"

The latest delegate estimates give Obama a modest lead over Clinton. The Associated Press count shows both candidates with about 1,200 committed delegates.

It takes 2,025 delegates to secure the Democratic Party's presidential nomination in the state-by-state primary and caucus balloting that will culminate in the party's national nominating convention in Colorado in late August.

Obama is favored in next Tuesday's contests in Wisconsin and Hawaii, while Clinton hopes to rebound in Texas and Ohio on March 4.

In the Republican presidential race, Senator John McCain of Arizona solidified his grip on the party nomination with convincing victories in Maryland, Virginia, and Washington, D.C.

Increasingly, McCain is turning his attention to the general election campaign against the Democrats.

"We do not yet know for certain who will have the honor of being the Democratic Party's nominee for president," he said. "But we know where each of their candidates will lead this country, and we dare not let them!"

Most estimates give McCain about 800 committed delegates, well on the way to the 1,191 required to win the Republican nomination.

Former Arkansas governor Mike Huckabee remains in the race and continues to draw conservative voters who oppose McCain's record on tax cuts and immigration.

The next Republican contest is Tuesday in Wisconsin.