WASHINGTON — Barack Obama won three modest but potentially consequential victories yesterday, beginning a stretch of primaries and caucuses that favor him in his back-and-forth battle for the Democratic presidential nomination with Hillary Rodham Clinton.

Republican front-runner John McCain, meanwhile, was reminded again on a sobering Saturday that he'll have to earn a fuller embrace from skeptics in his Grand Old Party. Former Arkansas Gov. Mike Huckabee continued his vibrant long-shot challenge, beating McCain in Kansas and Louisiana. McCain won a closely fought contest in Washington state.

But the spotlight was brightest on Obama, who decisively won caucuses in Nebraska and Washington and a primary in Louisiana. The final delegate winnings could push him into at least a virtual tie with Clinton, if not an outright lead.

Both Clinton and Obama are now more than halfway to the 2,025 delegates necessary to win.

The longer the contest goes on, the more likely it is that it could be decided by more than 400 "super delegates" — party elected officials and leaders — in a scenario that could anger supporters of one of the leading contenders.

But Obama vowed he would not let that happen.

"We won north. We won south. We won in between. And I believe that we can win Virginia on Tuesday if you are ready to stand for change," Obama told about 6,000 Democrats at a dinner last night in Richmond, Va.

Many in the audience responded, "Yes we can, yes we can."

He added: "We are going to be unified as Democrats, whoever the nominee is going to be."

Obama, a senator from Illinois, now looks forward to primaries in Maryland, Virginia and the District of Columbia on Tuesday. He is favored to win Maryland and the District of Columbia, partly because of their significant black populations.

But as he proved again yesterday, he also is strong in caucus-holding states with little diversity, such as Nebraska, that are a measure of the intensity of his support. Such victories have helped offset Clinton's wins in megastates like New York, California and New Jersey in last week's Super Tuesday.

Clinton, a senator from New York, is putting up a strong fight in Virginia, whose D.C. suburbs are more akin to the voters who carried her over the top in the big states. A victory over Obama in Virginia could blunt his momentum.

In a race this close, momentum could be a huge factor, especially in the next big-state tests March 4 in Texas and Ohio, and Clinton risks going without a significant victory for nearly a month leading into them.

In her speech to the same crowd in Richmond, Clinton aimed criticism at McCain.

"President Bush has already put his conservative stamp of approval on Senator McCain's credentials and I'm sure it should help," she told a crowd of about 6,000 in Richmond.

Huckabee ambushed McCain in Kansas caucuses and narrowly beat him in Louisiana's primary. But Louisiana Republican Party rules say that since no candidate appeared to get more than 50 percent, no delegates will be awarded to the winner. Instead, they will be awarded at a state convention next weekend. McCain won the third Republican race of the night, Washington's caucuses. None of the state's delegates will be awarded until next week.

The losses were another reminder that McCain faces skepticism among Republicans, even as he holds a formidable lead in delegates. He entered yesterday with about three-fifths of the 1,191 necessary to clinch the GOP nomination.

Huckabee vowed to fight on, despite being down 3-to-1 to McCain in delegates.

"Folks, I didn't major in math, I majored in miracles, and I still believe in those, too," Huckabee said at the Conservative Political Action Conference here. He guaranteed a victory in Texas on March 4, even though Texas Gov. Rick Perry has urged Huckabee to get out of the race to help McCain heal party divisions.

McCain's aides downplayed the thumping from Huckabee, calling it a small bump on an inevitable road to the nomination.

"We expected to fall short in Kansas today," McCain adviser Jill Hazelbaker said after the Kansas results came in. "To that end, it does not change where John McCain is."

Anti-abortion activists and other social conservatives have had a big role in the Kansas GOP, and some of Huckabee's supporters say his appeal to them was a key to his victory in yesterday's lightly attended caucuses. Kansas caucus goers backed Huckabee over McCain by more than 2-to-1, ignoring Kansas Sen. Sam Brownback's endorsement of McCain. Rep. Ron Paul, R-Texas, finished third.

Huckabee's campaign chairman, Ed Rollins, and manager, Chip Saltzman, sent reporters a memo yesterday outlining how Huckabee could still win the nomination.

"The Republican National Convention is seven long months away; a lot can happen in that much time. A lot will happen," they wrote.

But other Huckabee supporters realize that McCain's delegate lead makes a Huckabee nomination unlikely. Tuesday's primaries in Maryland, Virginia, and the District of Columbia are likely to push McCain closer to clinching the GOP nomination, although Huckabee hopes to win in Virginia after winning five Southern states on Super Tuesday.

"We don't have any delusions. We know it is a long road and Huckabee is the underdog of underdogs," said Lucas Roebuck, a spokesman for the Internet group HucksArmy.com, which is separate from the campaign.

The next fight for the Democrats is today in Maine, which holds caucuses. Then comes Tuesday's "Chesapeake Primary" for both parties.

Clinton and Obama have campaign stops planned in Maryland and Virginia in the final two days. In addition, former President Bill Clinton is expected to campaign in Maryland today after attending morning services at two black churches in Washington.

McCain and Huckabee are both expected to have campaign appearances in Virginia tomorrow.

The Associated Press contributed to this report. Contact GNS Political Writer Chuck Raasch at craasch@gns.gannett .com.