The Rat Pack was the nickname given to a group of young, high-profile Canadian Liberal opposition Members of Parliament during the Progressive Conservative government of Prime Minister Brian Mulroney.
The Liberal Party had suffered the worst defeat in its history in the 1984 election. In the first years of the Mulroney government, the Liberals failed to mount an effective opposition to Mulroney, and were in danger of being overshadowed by the New Democratic Party (NDP), which had almost as many seats as the Liberals.
In the midst of this, a group of young, energetic, and unknown Liberals soon emerged as a vocal voice of opposition to Mulroney. They included Don Boudria of eastern Ontario, Sheila Copps of Hamilton, Brian Tobin of Newfoundland and John Nunziata of the Greater Toronto Area. Tobin had been elected when the Liberals regained power in the 1980 election; the others had been among the few bright spots for the Liberals in the 1984 blowout. Except for Nunziata and Boudria, who held some socially conservative views, all of them came from the left wing of the Liberal Party. Boudria, Tobin, and Copps were all appointed to Cabinet at various times during the ministry of Jean Chretien.