The Province of Ontario is governed by a unicameral legislature, the Legislative Assembly of Ontario, which operates in the Westminster system of government. The political party that wins the largest number of seats in the legislature normally forms the government, and the party's leader becomes premier of the province, i.e., the head of the government. Ontario's primary political parties are the centre-left Ontario Liberal Party, the centre-right Progressive Conservative Party of Ontario (PC), and the social democratic Ontario New Democratic Party (NDP). The Green Party of Ontario has seen its support grow over the years - to 8.1% of the vote in 2007 - but has yet to win a seat in the Legislature.