Bulgaria is a parliamentary democracy where the prime minister is the head of government and the most powerful executive position. The political system has three branches—legislative, executive and judicial, with universal suffrage for citizens at least 18 years old. The Constitution also provides possibilities of direct democracy, namely petitions and national referenda. Elections are supervised by an independent Central Election Commission that includes members from all major political parties. Parties must register with the commission prior to participating in a national election. Normally, the prime minister-elect is the leader of the party receiving the most votes in parliamentary elections, although this is not always the case.