Italy achieved political unity as a nation in 1861 under the Royal House of Savoy. Following the defeat of dictator Benito Mussolini's regime during World War II, a republican form of government was adopted in 1946. There have been two republics in postwar Italy, beginning in June 1946 and April 1994, respectively. In 1993, Italy made major changes to its electoral system: three-fourths of the seats in parliament would be filled by simple majority vote, and the remainder would be allocated by proportional representation to those parties securing at least 4% of the vote. According to the constitution, power is shared between executive, legislative, and judicial branches. The popularly elected bicameral parliament consists of a 315-member Senate and a 630-member Chamber of Deputies, both elected to five-year terms. Parliament is subject to dissolution by the president or by a vote of no-confidence when a new government cannot be formed. Twenty-one national parties presently dominate Italian politics.
The prime minister is nominated by the president of the republic (currently Carlo Azeglio Ciampi) and forms a government and political agenda that must be approved by both chambers of parliament. The prime minister is the head of government and must retain the confidence of parliament, either through governing majorities or benign political consent. The prime minister's power has been limited in the past by divisions among the many political factions within parliament. Italy has had 59 governments since 1945. The current prime minister is Silvio Berlusconi, who arrived at the job on 10 June 2001 after being appointed by President Carlo Azeglio Ciampi.