WASHINGTON — Barack Obama's march toward the Democratic presidential nomination picked up support from four more superdelegates yesterday, pushing him ever closer to victory over Hillary Rodham Clinton.

Clinton added two superdelegates.

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.

The Associated Press interviewed more than 70 undeclared superdelegates or their representatives yesterday, 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.

She picked up two superdelegates 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 she lost another supporter, Virginia state House member Jennifer McClellan, one of at least nine superdelegates who have switched to Obama.

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.