Senate Democrats have dropped a key proposal from the Employee Free Choice Act, a bill that would make it easier for workers to join unions. On Thursday, Senate negotiators said they would drop a card-check provision that would require employers to recognize a union if a majority of workers signed cards in favor of unionization. Labor groups had made card-check their top priority in the bill’s passage. But the provision came under intense opposition from business lobbyists, swaying several so-called “moderate” Senate Democrats.