play (one's) ace (card)
To make use of a resource that one knows or hopes will ensure a decisive and successful outcome. She played her ace card during the debate by bringing up her opponent's earnings from investment firms that contributed to the global recession just a few years prior. The prosecutor then played his ace, showing security camera footage clearly placing the suspect at the scene of the crime.
play your ace
If you play your ace, you do something clever and unexpected which gives you an advantage over other people. Note: In many card games, the ace is the card with the highest score. He told us that he was a very important criminal lawyer who had defended men on heavy charges. And then he played his ace. He also had a number of clients who were involved in the gold business.
play your ace
use your best resource.play your ˈace
use your best argument, etc. in order to get an advantage in a situation: I think it’s time we played our ace, which is the fact that without us they wouldn’t be able to run this place.This expression refers to card-playing. The ace usually has the highest value, and is associated with success.