Updated

Barack Obama and John McCain swept the Potomac Primaries Tuesday, giving the candidates a vital injection of delegates in the race for their respective party nominations.

McCain easily beat Mike Huckabee in Maryland and the District of Columbia after starting out the night in a surprisingly close race in Virginia that later opened up to a large win.

The GOP front-runner's victories helped in rebound after he suffered embarrassing defeats Saturday to underdog Huckabee in Louisiana and Kansas.

But for Obama, the victories in the three contests capped a week-long shutout over Hillary Clinton, and for the first time since the race began gave him a lead in the delegate counts. Associated Press tallies showed Obama with 1,212 and Clinton with 1,191.

With the District of Columbia victory, Obama has won eight consecutive races since Saturday, and could top that with two more next Tuesday in Hawaii and Wisconsin.

At a rally in Madison, Wis., Tuesday night, Obama said his streak should blunt the comments of critics who doubt his campaign's staying power.

"Though we won in Washington, D.C., this movement won't stop until there's change in Washington, D.C., and tonight we're on our way," he said. "At this moment, the cynics can no longer say that our hope is false — we have now won East and West, North and South, across the heartland."

Click here to see state-by-state results from the primaries.

Obama and McCain were the favorites going into the day's contests, where 168 delegates for the Democrats and 113 delegates for the Republicans were up for grabs. Virginia was the biggest prize for both parties.

Clinton had already moved beyond the races, speaking at a packed rally Tuesday night at the University of Texas in El Paso, where she did not once mention the day's losses. She's banking on the March 4 primaries — Ohio, Texas and Rhode Island and Vermont — to reverse Obama's momentum from the February contests.

In Texas she focused on the economy, health care and immigration — pushing domestic issues she hopes will win her support with her Latino base along the Mexican border.

"I'm tested, I'm ready, let's make it happen," she said. "We're going to give our young people not only confidence and optimism but real results."

Click here to read more about Clinton's appearance in El Paso, Texas on primary night.

McCain is sitting pretty in the delegate count but still has ground to make up with conservatives. Virginia exit polls showed Huckabee doing well among very conservative voters, who appeared to have turned out in large numbers in the western part of the state. Fifty-two percent of voters said McCain was not conservative enough.

Virginia returns showed the Republicans nine points apart, McCain at 50 percent and Huckabee at 41 percent. The returns showed Obama with 64 percent and Clinton with 35 percent, with 100 percent of precincts reporting.

The Maryland and D.C. primaries also appeared to give both winners huge margins of victory, with Obama scoring 3 to 1 over Clinton in the nation's capital and nearly doubling her, 61-35, in Maryland. McCain scored 4 to 1 over Huckabee in the District of Columbia and more than 20 points over the Arkansas governor in the Maryland race.

The McCain camp showed a bit of humility along with his unwavering confidence.

"We are approaching the end of the first half of this election on quite an upswing," McCain said in Alexandria, Va., commending Huckabee for running a "formidable" campaign.

"I've got to say: He certainly keeps things interesting," he said.

Campaign manager Rick Davis said in a statement, "John McCain will be the Republican nominee for president. He will continue to campaign hard in the coming contests across the country and unify the Republican Party for victory in November."

FOX News exit polls showed Obama gaining traction in Virginia among voting blocs that typically favor Clinton.

Polls showed 58 percent of women favored Obama while 42 percent favored Clinton. Fifty-three percent of seniors went for Obama, while 47 percent went for Clinton. Hispanic voters went for Obama over Clinton by a split of 55 to 45 percent. And among white voters, Clinton still had an edge, but a narrow one. Fifty-one percent went for Clinton, and 48 percent went for Obama.

Obama also had the support of more than 90 percent of black voters, a group that has consistently gone for him, but in ever increasing margins.

Clinton has suffered down a streak of negative headlines since Super Tuesday basically ended in a draw. She lost the weekend contests, replaced campaign manager Patti Solis Doyle and lent herself $5 million before funding kicked up again.

Clinton's delegate lead was only razor-thin going into Tuesday's contests — 1,147, compared to 1,124 for Obama — in the race for the 2,024 delegates currently needed to win the Democratic nomination at this summer's convention.

On the GOP side, an Associated Press tally showed McCain has 789 delegates to Mike Huckabee's 241 delegates. It takes 1,191 delegates to clinch the GOP nomination.

The Potomac victories help McCain recover and resume his role as the presumptive nominee. Since the Virginia GOP contest was winner-take-all, McCain gets all 60 delegates in the state, leaving Huckabee with the to-impossible task of beating him.

Weekly Standard Publisher William Kristol said that the win in Virginia by McCain — who is strongly suspicious to conservatives — isn't as harrowing as it seems at first blush.

"If you were king of the Republicans and could nominate an electable nominee for the general election, you'd probably want someone who was acceptable to conservatives, but a little less conservative than about half the party. So, in a funny way having 52 percent of the party say 'I'm more conservative than McCain,' isn't so bad if you're trying to win a general election with a lot of moderates," he said.

Since Mitt Romney dropped out of the race last week, McCain has been the favorite to win given his impressive delegate tally, but Huckabee has repeatedly pledged to stay in, saying he's more into "miracles" than mathematical odds.

Huckabee teased the pundits Tuesday evening in Little Rock, Ark.

"On one hand, you have the pundits saying that I'm really not a factor and on the other hand, boy, I'm gonna make it really hard for John McCain," he said. "Well, it can't be both, you gotta pick one or the other, so pick which one it is. If I'm a significant factor that's really messing it up for him or if I'm an absolute insignificant irritation and just sort of an aside, but I can't be both things at the same time — that's not possible."

The former Arkansas governor's wins over the weekend show he's still got support among base voters who are waiting for McCain to offer some solid evidence of his conservative principles.

Turnout in all three Democratic contests was high, with the open primary in Virginia resulting in Democrats getting more than 320,000 votes more than in the GOP contest. In D.C., more than 112,000 people voted in the Democratic race compared to less than 5,000 in the Republican primary there.

Polls were originally set to close at 8 p.m. ET in Maryland, but state elections chief Linda Lamone got a court order to extend voting statewide for 90 minutes — until 9:30 p.m. — because of traffic problems caused by bad weather.

Interest in the close Democratic contest was evident from spikes in voter registrations and absentee balloting in the region.

In Virginia, a total of 32,166 people had requested mail absentee ballots by last Tuesday's deadline, and nearly two-thirds of them were for Democratic primary ballots. In the first two weeks of the year, 37,025 people met the Jan. 14 deadline for registering in time to vote in the primaries. Of that, 61 percent of the new registrants were age 24 or younger.

In the District, voter registration increased by 34,916 to 377,007 since the presidential primary in January 2004 — and is up more than 93,000 compared with the 2000 primary.

FOX News' Bonney Kapp and Aaron Bruns and The Associated Press contributed to this report.