Senate Republicans say they're confident they can force a vote on a measure to overturn a new federal rule that makes it easier for workers to organize into unions.

Sen. Johnny Isakson (R-Ga.) said he will have enough votes on a discharge petition to bring up for a vote the resolution of disapproval he's offered to reverse a National Mediation Board ruling that changes how union elections are held.

"We will have the signatures necessary to discharge my resolution of disapproval, to bring about a vote on the floor of the Senate," Isakson said during an appearance on Fox News.

30 votes are needed to discharge the bill to the Senate floor; there are 41 Republicans in the Senate. Since resolutions of disapproval cannot be filibustered, the Senate could pass the resolution with only 51 votes.

"If it's a partisan vote, we'll lose," Isakson said of the vote on the resolution. "If it's a pragmatic, thoughtful vote, we'll win."

Even if it were unsuccessful, forcing a vote would have the effect of putting some centrist Democrats in a tough spot between difficult reelection and primary battles this year and organized labor supporters who have aligned themselves often with Democrats in recent elections.

At issue is a change the board made to rules this week on union organizing. The new rule allows unions to organize workplaces with a simple majority vote of workers who are present for a given vote. Before, members of a workplace who did not participate in a union election were assumed to be votes against organizing.

Isakson said the rule was "to do card check by running around the back door, and that's not right."

Republicans have opposed that legislation, the Employee Free Choice Act (EFCA, or "card check") successfully so far this Congress, despite labor's best efforts to pass the legislation in some form.