until the fat lady sings

Until a given situation, event, effort, etc., is completely finished or concluded. Usually used in the phrase "it's not over until the fat lady sings" or "it ain't over until the fat lady sings." It is often used in reference to organized competitions, such as sporting events, political elections, etc. A: "We're down by six points with only two minutes remaining. There's no way we can win now!" B: "Hey, it's not over until the fat lady sings!" It's not looking likely that the senator will be elected to another term, but it ain't over until the fat lady sings.