From the American Interest:
According to Sheet Metal Workers Local 85 Union in Atlanta, Obamacare’s requirements “will add between 50 cents to $1 an hour to the cost of members’ compensation package,” making them less competitive than non-unionized contractors with fewer than 50 employees, who can forgo health care for their workers without fear of a penalty. Unions who once thought Obamacare would save them money are now aggressively lobbying the Obama administration to fork over federal subsidies. This request has caught Obama in a bind.
I'm guessing that Obama does not feel himself particularly bound, because he doesn't actually regard beefy white guys in windbreakers as long-run members of his coalition. His plan has always been to string the unions along until such time as non-white immigration makes them irrelevant.