(CNN) - Barack Obama picked up four more superdelegates Thursday, his campaign announced.
Washington Rep. Jim McDermott, California Rep. Henry Waxman, California Rep. Henry Berman and Communications Workers of America President Larry Cohen will all cast their superdelegate votes for the Illinois senator.
Waxman and Berman both have ties to the Clintons, and many of their prominent supporters in California are supporters of Hillary Clinton.
The CWA said Thursday that Cohen's endorsement is a personal one and does not signal an endorsement by the union, which decided last year that it would not back a candidate. In a Thursday release, the union said that decision would be re-visited at its June convention.
According to CNN's estimate, Obama now has 291 superdelegates to Clinton's 274.