"Heritage Action cannot support a budget deal that would increase spending in the near-term for promises of woefully inadequate long-term reductions," the group said in a statement. "While imperfect, the sequester has proven to be an effective tool in forcing Congress to reduce discretionary spending, and a gimmicky, spend-now-cut-later deal will take our nation in the wrong direction."
The group's leader, Michael Needham, said on Twitter that it isn't unequivocally opposed yet. "We have an open, but not empty, mind," he said.
The statement leaves some wiggle room, pending the final deal, but it could spell trouble for the proposal in the House, where Heritage Action and like-minded groups have strong influence among GOP members.