A half-dozen senators friendly to labor have decided to drop a central provision of a bill that would have made it easier to organize workers.

The so-called card-check provision  which senators decided to scrap to help secure a filibuster-proof 60 votes  would have required employers to recognize a union as soon as a majority of workers signed cards saying they wanted a union. Currently, employers can insist on a secret-ballot election, a higher hurdle for unions.

The abandonment of card check was another example of the power of moderate Democrats to constrain their party’s more liberal legislative efforts. Though the Democrats have a 60-40 vote advantage in the Senate, and President Obama supports the measure, several moderate Democrats opposed the card-check provision as undemocratic.

In its place, several Senate and labor officials said, the revised bill would require shorter unionization campaigns and faster elections.