"former Liberal member Peter Costello" considerably undereggs the situation. He was deputy federal leader of the Liberals for 13 years, 11 of those as Treasure

"former Liberal member Peter Costello" considerably undereggs the situation. He was deputy federal leader of the Liberals for 13 years, 11 of those as Treasurer in Government. He remained a powerful factional leader for years after that, and as far as I'm aware is still a party member.