WASHINGTON - Barack Obama erased Hillary Rodham Clinton's once-imposing lead among superdelegates Saturday when he added more endorsements from the group of Democrats who will decide the party's nomination for president.

Obama added superdelegates from Utah, Ohio and Arizona, as well as two from the Virgin Islands who previously had backed Clinton. The additions enabled Obama to surpass Clinton's total for the first time in the campaign. He had picked up nine endorsements Friday.

The milestone is important because Clinton would need to win over the superdelegates by a wide margin to claim the nomination. They are a group that Clinton owned before the first caucus, when she was able to cash in on the popularity of the Clinton brand among the party faithful.

Those party insiders, however, have been steadily streaming to Obama since he started posting wins in early voting states.

"I always felt that if anybody establishes himself as the clear leader, the superdelegates would fall in line," said Don Fowler, a former chairman of the Democratic National Committee.

"It is perceived that he is the leader," said Fowler, a superdelegate from South Carolina who supports Clinton. "The trickle is going to become an avalanche."

Superdelegates are the party and elected officials who will automatically attend the Democratic national convention this August in Denver. They can support whomever they choose, regardless of what happens in the primaries.

They are key because neither Obama nor Clinton can win the nomination without them.

Nearly 800 superdelegates will attend the convention. Obama has endorsements from 276, according to the AP. Clinton has 271.5.