Canada has a multi-party system in which many of its legislative customs derive from the unwritten conventions of and precedents set by the Westminster parliament of the United Kingdom. The country has been dominated by two parties, the centre-left Liberal Party of Canada and the centre-right Conservative Party of Canada. The historically predominant Liberals position themselves at the centre of the political scale, with the Conservatives sitting on the right and the New Democratic Party occupying the left. Smaller parties like the Quebec nationalist Bloc Québécois and the Green Party of Canada have also been able to exert their influence over the political process by representation at the federal level.