“You’re no Jack Kennedy” is a phrase used to deflate politicians who are perceived as thinking too highly of themselves.
The words come from the 1988 vice presidential debate between Sen. Lloyd Bentsen (D-TX) and Sen. Dan Quayle (R-IN). When Quayle compared his relative youth to that of former President John F. Kennedy, Bentsen shot back, “Senator, I served with Jack Kennedy, I knew Jack Kennedy, Jack Kennedy was a friend of mine. Senator, you’re no Jack Kennedy.”
Washington Post: “If one will be remembered for a single remark, as the recently departed Lloyd Bentsen is, let it be for the perfect put-down. Most of us never get to experience the joy of excoriating an opponent with a dead-on, devastating riposte. We always think of it too late.”