Barack Obama has taken the lead in the race to become the Democratic Party's presidential nominee with a clean sweep of victories in the Potomac primary election.
Clear wins in Virginia, Maryland and the District of Columbia made it seven straight victories in four days for the young Illinois senator and took his tally of delegates higher than Hillary Clinton's for the first time.
The man who wants to be America's first black president said: "We have now won east and west, north and south, and across the heartland of this country we love."
Exact delegate figures are not yet known, but early estimates by CNN showed Mr Obama now had a total of 1,208, compared with Mrs Clinton's 1,185. Early AP estimates put it at 1,210 to 1,188 in Mr Obama's favour.
The race is so close, it could come down to superdelegates deciding the party's nominee at the national convention this summer.
But Mr Obama now hopes to build momentum from these wins through Wisconsin and Hawaii next week, and on to Texas and Ohio next month, where the former First Lady is concentrating her efforts.
Mrs Clinton made no reference to her string of defeats as she spoke to supporters as the results came in.
And in the Republican contest, the party's presumptive front-runner John McCain also produced a clean sweep of the three states, as Mike Huckabee pledged to fight on.
Exit polls in Virginia showed Mr Obama, 46, was on a roll, winning 90% of the African American vote, 58% of the female vote and even 48% of the white vote (Mrs Clinton won 51% in this last category).
In his victory speech, Mr Obama told supporters in Madison, Wisconsin: "You have lifted my spirits." To loud cheers, he said: "Tonight we're on our way, but we know how much further we have to go."
