Grover Norquist said today that he received a call from Arlen Specter’s chief of staff informing him that the Pennsylvania Senator will vote against cloture on card check, dealing a serious blow to big labor’s efforts to pass the legislation that would make it easier to form unions by denying workers a secret ballot on unionization.

Specter, who has received union backing in his past campaigns, did not support the Republican filibuster of card check last time it came up for a vote, and his support was seen as essential to passing the legislation this time around.

Norquist made the announcement during remarks at a labor conference sponsored by the Capital Research Center, and I confirmed them with our own Jim Antle, who is in attendence.

UPDATE: Specter makes it official.