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Democratic presidential candidate Sen. Hillary Clinton (D-NY) speaks about her plan to reward companies that create jobs in America, at the 21st Century Jobs Summit at the IBEW in Pittsburgh, Pennsylvania on April 2, 2008. (UPI Photo/Stephen Gross)

Clinton, already trailing Obama in the total popular vote and in money, is trying to keep her edge in the number of superdelegates who support her, the Los Angeles Times reported Friday. Superdelegates do not have to follow a state's primary results.

But Obama is attracting superdelegates because "his arguments are more persuasive," said Mark Mellman, an unaffiliated Democratic pollster.

"(Clinton) obviously hopes that's going to change," Mellman said. "But for now, his arguments are being more persuasive with those superdelegates."

Aides said they would prefer that superdelegates consider broad criteria, such as electability, rather than a state's popular vote when considering whether to support Clinton or Obama.

But that strategy may not be working.

U.S. Rep. Lynn Woolsey, D-Calif., a Clinton supporter, has committed to backing the candidate with the bigger share of the popular vote.

While pledging to remain a Clinton supporter, Woolsey said, "I will cast my vote at the convention for the candidate that is chosen not through back-room deals, but by the votes of the American public."