Sen. Bill Frist's decision to break with the president over stem-cell research annoyed Bush's aides. "He's changed his position on this before," said one senior Bush adviser, who declined to be identified so he could speak freely. Frist called Bush to alert him the night before he went public on the Senate floor. "I don't know how long he's been working on this, but he had left the impression with a lot of people that he was supporting the president's policy," the senior aide said. Frist's flip-flop has fired up Bush's supporters in the House, who are likely to block any attempt to override a veto. "This may have solidified it," the aide said.