Idiom meaning, usage examples, facts

1. The other team thinks they can win this basketball game, but that’s only because we haven’t put our best player in yet. He’s our ace in the hole
2. It looked like the politician would lose the debate until he brought up his ace in the hole , an argument that nobody could refute.

The expression originates from some forms of the card game poker, in which players have both community cards and private (“hole”) cards in their hands. To have an ace in one’s private hand means that one can win the game without others suspecting ahead of time.