Since Confederation, the only formal coalition government at the Federal level was during Canada's involvement in World War I, when the governing Conservatives rebranded as the Unionist Party and accepted Liberals from English Canada into government in response to the Conscription Crisis of 1917. Previous Progressive Conservative and Liberal minority governments had relied on ad hoc voting arrangements with the NDP and the former Social Credit Party to maintain supply instead of formal coalitions. Pierre Trudeau's private offer of a coalition to the NDP after the 1980 election, an attempt to form consensus in the patriation debate and bring more Western Canadian members into Cabinet, was refused by NDP leader Ed Broadbent.