WASHINGTON - Barack Obama has overtaken Hillary Rodham Clinton in superdelegate endorsements for the first time, according to The Associated Press calculations.

Obama picked up four superdelegate endorsements, including two from the Virgin Islands who had previously endorsed Clinton. The additions erased Clinton's once-imposing lead among the party and elected officials who will automatically attend the party's national convention this summer.

NBC still gives Clinton a slight edge in superdelegates. NBC’s estimated superdelegate count stands at 276.5 for Clinton and 274 for Obama. NBC's national delegate count currently stands at 1,426 for Clinton and 1,590 for Obama.

That leaves 246.5 superdelegates undeclared, according to NBC's count. Almost 50 are not yet named.