A pair of business and environmental organizations are mounting an advertising blitz against GOP senators that they hope will break the impasse over Environmental Protection Agency nominee Gina McCarthy.

Republican senators have placed a hold on McCarthy’s nomination, and there are rumblings that the party might filibuster her nomination when it comes to the floor.

The groups are trying to ward off that possibility by pressuring GOP lawmakers who have in the past supported or been linked to centrist or liberal energy policies.

The Sierra Club is the latest group to enter the fray with an ad campaign in Phoenix and Cincinnati that runs through July 15.