Barack Obama's march toward the Democratic presidential nomination picked up support from four more superdelegates Wednesday, pushing him ever closer to victory over Hillary Rodham Clinton — even as their primary marathon staggered on.

She added two superdelegates herself in what has become the last big contest as their race winds toward a finish.

There are just 217 delegates to be chosen in the final six primaries, and neither candidate can win enough of them to claim final victory. Meanwhile, 265 additional delegates — the party elders and other "superdelegates" — have yet to be claimed, and their support will be the deciding factor.

Though Obama padded his delegate lead in Tuesday's primaries, most uncommitted superdelegates still want to remain on the sidelines. The Associated Press interviewed more than 70 undeclared superdelegates or their representatives Wednesday, and many said they don't want to get involved until the voting ends June 3.

However, the comments of some of the uncommitteds were anything but encouraging for Clinton.

"I'm just wondering about the viability of Clinton's campaign at this point," said Laurie Weahkee, an add-on delegate from New Mexico. "I really want to hear from her more about if she wants to stay in the race — if the reason remains very concrete."

Pennsylvania Rep. Mike Doyle said Clinton's pitch to superdelegates has been that she can win the popular vote, but that was undercut when Obama netted more than 200,000 popular votes in the Tuesday contests.

"The math just got very tough for her after last night," Doyle said. "I think most of us out of respect for her are content to wait a little longer. ... The absolute best way for this to end is for the candidates to end it, not the superdelegates. That's the ending we all dream about every night."

She picked up two in the wake of Tuesday's loss in North Carolina and narrow victory in Indiana. North Carolina Rep. Heath Shuler had said he would support the winner of his district, and she won it handily. A spokeswoman for Texas labor leader Robert Martinez told the AP he is committed to Clinton, but it wasn't clear when he made the decision.

But she lost another supporter, Virginia state House member Jennifer McClellan. McClellan is one of at least nine superdelegates who have switched from Clinton to Obama since the Super Tuesday primaries on Feb. 5. There have been no public switches in the other direction.

"I think the time has come to support Senator Obama as the likely nominee," McClellan said in a conference call with reporters. "Given what happened last night, it's very unlikely we will have a different result, and it is time to come together as a party and prepare for victory against John McCain in November."

Obama also got the support of North Carolina Democratic Party Chairman Jerry Meek, North Carolina Democratic National Committee member Jeanette Council and California DNC member Inola Henry.

Clinton met with undecided superdelegates at Democratic Party headquarters Wednesday. She said, "We talked a lot about Florida and Michigan," two states that she won but don't have any delegates to count toward her total because their early primaries violated party rules. "I continue to emphasize and stress that we cannot disenfranchise those voters."

Clinton said later that she would be sending a letter to Obama and Democratic Party Chairman Howard Dean expressing her belief that seating the Florida and Michigan delegations is a civil rights and voting rights issue.

Obama was to make his pitch to the congressional fence sitters in meetings Thursday. He also planned to start traveling to swing states to signal that the general election has begun.

Superdelegates supporting Obama recently have given a number of reasons. They recognize he is the front-runner and want to end a divisive party fight. They were impressed with his handling of a crisis that confronted his campaign in the comments of his former pastor. They don't want to risk alienating black voters who are excited about Obama's chance to become the first black president. They simply think Obama would be a more attractive choice at the top of the ticket.

"I think that Senator Obama is going to be a tremendous boost for down-ballot races in North Carolina," Meek told the AP. "He's going to turn out segments of the electorate — particularly young people and African-Americans — who have historically low turnout levels. That will help candidates up and down the ballot."

Nancy Worley, Alabama's former secretary of state and the state Democratic Party's first vice chair, said she got calls Wednesday morning from Kansas Gov. Kathleen Sebelius and Virginia Gov. Tim Kaine — both Obama supporters.

"It appears that the Obama supporters, just from my perspective, are working a little harder at getting commitments," she said. Clinton's campaign has mainly used letters and e-mails, with occasional calls from staffers, she said, while Obama has used more of a "personal touch" with direct phone calls.

Nonetheless, she said she still hasn't been convinced one way or another even though she said she would be reluctant to vote against the pledged delegate leader. That is almost certain to be Obama.

Arizona Democratic Chairman Don Bivens also appeared closer to backing Obama after receiving e-mails from both camps Wednesday.

"The Obama one was more fulsome and sort of laid out the mathematical facts," Bivens said. He said the Clinton e-mails were from multiple individuals sharing why they thought she was the best choice.

"I'm still uncommitted, but I do believe that yesterday's results put me at a decisional plateau." He said the rest of the contests' outcomes are more predictable. "I think that we're at a point where the track got shorter and you can see the finish line."

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Associated Press writers Stephen Ohlemacher, Ann Sanner, Ben Evans, Kim Hefling and Liz Sidoti in Washington, Matt Mygatt in Albuquerque, N.M., Mike Baker in Raleigh, N.C., and Bob Lewis in Richmond, Va., contributed to this report.

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