upper hand, to have the

To have a position of advantage, power, and/or control (over someone, something, or some situation). The home team had the upper hand when their opponents' star quarterback went out with an injury. We've been doing everything we can for your father, but I'm afraid the cancer has the upper hand now.

To be in a dominating or controlling position. This term has been around since the fifteenth century. It comes from an ancient gambling game in which each player in turn puts one hand on a stick, beginning at the bottom, and the last one able to put his hand at the top wins. The Anglican Book of Common Prayer has it, “Up, Lord, and let not man have the upper hand” (from Miles Coverdale’s translation of Psalm 9:19).