WASHINGTON -- Barack Obama might keep calling himself the underdog. But from now on, that dog won't hunt.

His smashing victories in three Mid-Atlantic primaries yesterday will likely be seen as a turning point in the 2008 presidential contest.

Obama came roaring out of Maryland, Virginia and the District of Columbia with a new lode of delegates, taking the lead for the first time over Hillary Clinton, who once seemed all but unbeatable.

The latest results confirmed that Obama has continued to broaden and deepen his coalition, and he is now cutting into the heart of Clinton's base of support. Yesterday, for the first time, he pulled ahead of Clinton in delegates, according to an Associated Press tally.

John McCain, the likely Republican nominee, tipped his hat to the new Democratic front-runner last night.

"My friends, I promise you, I am fired up and ready to go," he told supporters, quoting Obama's campaign slogan on a night when McCain took the Maryland and District of Columbia primaries and dodged a potentially embarrassing loss to Mike Huckabee in Virginia.

Obama ran his winning streak to eight contests in a row, building impressive margins on both sides of the Potomac and winning a group that Clinton had owned - women voters. He won almost three in five women voters in Maryland and Virginia.

Obama also carried white men in both states, according to an Election Day survey of voters as they left polling places.

He lost the overall white vote in Maryland by a margin of 52 percent to 42 percent, one of his better performances among white voters this year. But in Virginia, a state that combines elements of the old South with a generous helping of suburban liberalism, he won 50 percent of the white vote, according to the exit poll.

The Illinois senator took a slice from the center of Clinton's coalition, peeling away supporters that her top strategist, Mark Penn, had described only the day before as her "core" voters: the working class, women and Roman Catholics.

Yesterday's contests were the latest twist on what could be a long road to the national convention in Denver in August. But there were few encouraging signs for Clinton, whose campaign shake-up continued with the departure of deputy manager Mike Henry.

Among the rare bright spots for Clinton: White voters who described themselves as Democrats, as opposed to independents or Republicans, favored her in both Maryland and Virginia, but they made up less than half the primary vote in each state. She carried white women and all white voters 45 and older in Maryland.

Clinton's campaign argued this week that she had "repeatedly confounded pollsters" by doing better than expected on Election Day, but yesterday the reverse was true.

At the same time, McCain smoothed his path to the fall vote with a triple victory, despite an apparent lack of enthusiasm from his party. Many Republicans, particularly moderates, stayed home or, in Virginia, crossed over to back Obama in the Democratic primary.

The results might have hastened the time when Huckabee decides to abandon his campaign. But almost half of Republican voters in Maryland and Virginia said McCain's views aren't conservative enough. In Maryland, about three in 10 of those who were unsatisfied with his conservatism voted for McCain anyway.

McCain's challenge in uniting his party pales beside Clinton's increasingly uphill fight to stop Obama. She faces possible defeats next Tuesday in Obama's native state of Hawaii and in Wisconsin, a swing state where the outcome could be close.

It wasn't remotely close on the shores of the Chesapeake. Obama carried every income group in Maryland.. He won a majority of the Catholic vote in Virginia, and in Maryland, where more than one in five Democrats are Catholics, he took 45 percent to Clinton's 48 percent.

His support among fellow African-Americans has become almost monolithic. Blacks cast 37 percent of the Democratic vote in Maryland, and Obama won 84 percent of their votes. He won 90 percent in Virginia, where blacks made up 30 percent of the Democratic electorate.

Obama trounced Clinton by more than a quarter-million votes in Virginia.

In Maryland and Virginia, a majority of Democratic voters said that they wanted a candidate who could bring about change, and Obama carried that group by better than five to one. Relatively few voters, only about one in five, said experience was more important, and virtually all of them were Clinton voters.

As the Democratic contenders try to set the stage for the next phase of their race, they are looking at the contest through different lenses.

Obama's campaign sees the primaries and the caucuses as the decisive phase of the race. The candidate who wins the most pledged delegates "will in all likelihood end up being the nominee of the party," David Plouffe, the Obama campaign manager, said yesterday.

Obama's theory is that the hundreds of elected Democratic officials and party activists who are automatic delegates to the convention will swing behind the candidate who came out ahead during the primary phase, which lasts until June.

"We have a healthy, pledged-delegate lead right now, and we intend to build on it and grow it," said Plouffe.

The Clinton camp, however, is making the point that the superdelegates, as these automatic delegates are known, are free agents for a reason: Their job is to back the candidate they think has the best chance of winning the White House.

Penn, the chief Clinton campaign strategist, argued in a memo this week that the New York senator is the Democrat with the best chance of defeating McCain in November.

"She will neutralize the argument on national security so the election will turn on her ability to manage our economy and reform health care," Penn wrote. Negative attitudes toward Clinton, he added, have already been factored into voter decisions about the fall race, with polls showing a dead heat between McCain and Clinton.

By contrast, the Clinton campaign memo warned, the GOP "attack machine" would "redefine" Obama, if he became the nominee. According to Penn, Obama would see his "negatives" go up, and his chances of carrying key states in the general election will "erode" or "may even crumble."

Clinton is putting her emphasis on big-state contests in Ohio and Texas on March 4, and in Pennsylvania on April 22.

More than 30 states have voted, and Obama has finished first in far more states throughout the country. With his victories yesterday, he has won 21 states to Clinton's 10, including all six since Super Tuesday.

paul.west@baltsun.com