In the wake of Sen.-elect Scott Brown’s (R) stunning victory in Massachusetts, union officials on Wednesday are acknowledging privately that the flip of late Sen. Edward Kennedy’s (D-Mass.) seat likely dooms “card check— legislation.

“They were in the midst of deciding what they believed would get 60 votes and we were confident it was going to be a strong bill,— an AFL-CIO official said Wednesday morning of the ongoing Senate negotiations on an Employee Free Choice Act compromise. “With 59 Democrats — assuming the Republicans are going to filibuster — any version of labor law reform, they’re going to have to reach out— to Republicans.

But enlisting even one GOP Senator to rewrite the nation’s labor laws in line with union demands would likely be impossible. Senate Minority Leader Mitch McConnell (R-Ky.) has said EFCA will “fundamentally harm America,— and the U.S. Chamber of Commerce and other business groups remain dead-set against the labor-backed proposals.

Even with a filibuster-proof Democratic majority prior to Tuesday’s special election, Democratic leaders continued to flounder on enlisting moderates such as Sen. Blanche Lincoln (D-Ark.) to get on board with a compromise bill.

Just last week, AFL-CIO President Richard Trumka predicted that a “card check— bill would reach President Barack Obama’s desk by April 1.

But now labor leaders are expected to resume closed-door negotiations with Democratic Congressional leaders later this week to discuss the status of EFCA and the now-fragile health care legislation. A source familiar with ongoing health care and labor negotiations said Tuesday’s election was a game-changer for both issues but that labor’s marquee legislative priority is likely to be the biggest casualty of Bay State Attorney General Martha Coakley’s loss.

“Card check is dead,— the source said.