(sitting) in the catbird seat

In a powerful or influential position. The phrase likely refers to the catbird's preference for high tree branches (a position that helps it to avoid predators). As the CEO's assistant, you are definitely sitting in the catbird seat. I know you were hoping to be elected president over Joe, but, as vice president, you're in the catbird seat if he resigns.

Sl. in a dominant or controlling position. Sally's in the catbird seat—telling everybody where to go. I hold all the aces. I'm in the catbird seat.

Being in a position of advantage or superiority. The term originated in the American South, where the catbird is quite common. It is thought to allude to the bird’s habit of singing from a very high perch in trees. It came into common usage in the 1940s when Mississippi-born sportscaster Red Barber would use it, for example, for a pitcher who was almost certain to strike out all the batters. Barber said he himself first heard the term in a poker game where he had bluffed all but one player into dropping out, but the remaining player, who had said from the start that he was sitting in the catbird seat, proved to have an ace and an ace in the hole. James Thurber used the expression as the title of a short story about a mild-mannered accountant who was so irritated by a colleague using this and other terms that he planned to murder her.