Sen. Barack Obama celebrated another decisive sweep Tuesday night, winning the Potomac primary in Virginia, Maryland and the District of Columbia, determined to erode or even erase Hillary Rodham Clinton's delegate lead in the Democratic presidential race.

Obama's triumph made it six straight over Clinton, the former first lady, now struggling to keep up in a race she once commanded. Obama has now won 21 states, Clinton 10.

"Barack Obama is a metaphysical force in American politics," Democratic strategist Donna Brazile, said on CNN Tuesday night. For Clinton, Brazile asked, "Where is the joy? Campaigns are supposed to be about joy." Brazile added it may now be difficult for Clinton to stop Obama’s "wave of support."

Interviews with voters in Virginia showed blacks accounted for nearly one-third of the ballots cast in Virginia, and Obama's share approached 90 percent. He and Clinton split the white vote.

In Maryland, Obama won 62 percent to 35 percent; in Virginia, 64 percent to 35 percent, and in D.C., Obama crushed Clinton, 76 percent to 24 percent.

Candice Tolliver, a spokeswoman for the Obama campaign, told BlackAmericaWeb.com exit polls reported that Obama won 50 percent of white voters in Virginia.

In all, there were 168 delegates at stake in the three Democratic primaries. Obama, according to CNN, now leads Clinton in the delegate count 1,215 to 1,189. Both are far from the 2,025 needed to win the nomination at the Democratic National Convention this summer.

Peter C. Groff, a Colorado state senator, publisher of Blackpolicy.org and executive director of the Center for African-American Policy at the University of Denver, said the Potomac primary ended what's become an impressive week for Obama overall: Obama won 13 out of 22 states on Super Tuesday; won eight in a row since then; he has the potential of winning Wisconsin and Hawaii on Feb. 19 before Texas and Ohio on March 4.

"Conceivably, he could win 11 in a row," Groff told BlackAmericaWeb.com. "The other big story is the size of the Obama margins over Clinton. These aren't tight numbers. These are numbers showing that he's strong across all demographics.

"The Potomac primary wins may have started to defy conventional expectations regarding his strength in the Latino community; there are indications that he did well in Latino pockets in Maryland and Virginia," said Groff. "He's doing well in locations where he wasn't expected to do well."

"He clearly has the momentum in the race while the Clinton campaign appears shell-shocked," Groff said. "The Clinton campaign has identified Texas as the firewall, thereby becoming a regional candidate rather than a national candidate. She'll need something significant to jumpstart her campaign. Firing the campaign manager and having the deputy campaign manager resign shows the public signs of turmoil."

Obama has campaigned before huge crowds in recent days, and far outspent his rival on TV advertising in the states participating in the regional primary.

He began airing commercials in the region more than a week ago, and spent an estimated $1.4 million. Clinton began hers last Friday, at a cost estimated at $210,000.

The Clinton campaign maintains they never thought they would do well Tuesday and, instead, is looking ahead to Texas, Ohio and Pennsylvania.

But next stop in the primary sweepstakes is Wisconsin, where Obama spoke to a cheering crowd of thousands Tuesday night.

"The change we seek swept through Chesapeake and over the Potomac," Obama told supporters Tuesday night. "We won the state of Maryland. We won the commonwealth of Virginia. And though we won in Washington, D.C., this movement won't stop until there is change in Washington, D.C. And tonight, we're on our way."

"Another sweep," Craig Kirby, a Democratic strategist, told BlackAmericaWeb.com. "America, along with the Democratic Party, should now realize that change is happening."

"What has happened in the past eight days has awakened lots of people," said Kirby. "People who once thought they had no chance to participate now see and understand that they can participate. And, more importantly, this encouragement is beginning to blossom everywhere."

Meanwhile, the Clinton campaign hit yet another snag Tuesday night: Clinton’s deputy campaign manager resigned Tuesday, the latest departure in a staff shake-up follows string of losses to Obama.

In an e-mail message to staffers, Mike Henry said he was stepping down to allow campaign manager Maggie Williams to build her own team. Williams replaced Patti Solis Doyle during the weekend. Solis Doyle had recruited Henry to join the campaign last year.

"Out of respect for Maggie and her new leadership team, I thought it was the best thing to do," Henry wrote. "As someone who has managed campaigns, I share the unique understanding of the challenges that the campaign will face over the next several weeks. Our campaign needs to move quickly to build a new leadership team, support them and their decisions and make the necessary adjustments to achieve the winning outcome for which we have all worked so hard for over a year now."

It was unclear whether Henry was forced out.

According to CNN, "for the second election night in a row, Hillary Clinton failed to acknowledge or congratulate Barack Obama after he won the day in dominating fashion. ... The courtesy of conceding a primary or caucus loss -- and then congratulating your opponent -- is by no means required. But it has become standard practice during campaign season."

"Clinton congratulated Obama and John Edwards after their first and second place finishes in the Iowa caucuses," CNN reported. "Obama returned the favor in New Hampshire, saying Clinton "did an outstanding job." That courtesy continued through the early states. But as the race has shifted to a delegate chase with dozens of states in play around the country, the notion of congratulating one’s opponent seems, for Clinton, to have fallen by the wayside."

Trying to overcome a string of losses and a staff shake-up, Clinton sought new energy Tuesday night from a boisterous crowd of about 12,000 in Texas, a state she hopes will provide a rebound in her quest for the Democratic presidential nomination.

Clinton, whose rallies had been overshadowed by rival Barack Obama's huge crowds, arrived at the packed University of Texas at El Paso basketball arena as voters were giving Obama victories in Maryland, Virginia and Washington, D.C.

But her sights were set on the March 4 primaries and on President Bush.

"I'm tested, I'm ready, let's make it happen," she yelled to cheering supporters.

On the Republican side, Republicans John McCain and Mike Huckabee struggled over 116 delegates in the GOP primaries in the so-called Potomac Primary contests.

In Virginia, nearly seven in 10 voters in the Republican primary called themselves conservatives, and Huckabee was gaining half their votes in a strong challenge to the party's front-runner.

The surveys were conducted by Edison Media Research and Mitofsky International for The Associated Press and the television networks. There was no survey conducted in the District of Columbia.

The AP count showed McCain with 729 delegates. Former Massachusetts Gov. Mitt Romney, who dropped out of the race last week, had 288. Huckabee had 241 and Texas Rep. Ron Paul had 14.

It takes 1,191 delegates to clinch the Republican nomination, and McCain appears to be on track to reach the target by late April.

"Clearly McCain has a problem when looking at the numbers tonight," Groff said. "What's most incredible about it is that Huckabee is staying in the race -- why stay in the race when your party needs healing?

"There is a need for the party's deep base to galvanize around the nominee. Could Huckabee be raising a long term plan to have a more powerful presence in the GOP? Could he be campaigning for V.P.? Is he going for a third party candidacy?" Groff said.

"Perhaps Huckabee is thinking that he can continue winning states and keep McCain just short of the 1,191 delegates needed to win the nomination," he added. "Perhaps, in an open and brokered convention in St. Paul, he is able to persuade delegates to bolt for him while McCain lacks overall delegates." 

With Clinton facing a series of possible defeats, and Obama riding a wave of momentum, the two camps debated which contender is more likely to defeat McCain in the general election.

An Associated Press-Ipsos poll found Obama with a narrow lead over the Arizona senator in a potential match-up, and Clinton running about even.

"We bring in voters who haven't given Democrats a chance" in the past, said Obama pollster Cornell Belcher, citing support from independents.

Mark Penn, Clinton's chief strategist, countered that she holds appeal for women voters and Hispanics. "Hillary Clinton has a coalition of voters well-suited to winning the general election," he said.