During the Tokugawa Period, prior to the Meiji Restoration in 1868, Japan isolated itself from the rest of the world. During that time, Japan experienced cultural, social, and political development, which underscores the country's major differences with its neighbors to this day. The drafting of the Meiji Constitution in 1889 created the initial framework for parliamentary government.
After World War II, Japan underwent an American-led occupation, which democratized and secularized the nation. Political transformation during that period included the introduction of universal suffrage, the creation of a constitutional monarchy, and a purge of the economic and political elite responsible for Japan's aggression before and during World War II. The present Constitution, dubbed the "MacArthur Constitution" (after U.S. General Douglas MacArthur), was promulgated in 1947 during the U.S. occupation of Japan and has never been formally amended despite its foreign origins.
According to the Constitution, the national legislature is the supreme organ of the state. The bicameral legislature, or Diet, is composed of the House of Councillors (HC or Sangiin) and the more powerful House of Representatives (HR or Shugi-in). The 480 members of the HR are elected to four-year terms through a modified proportional representation system, in which 300 members are chosen from single-member districts, and 180 are chosen proportionally in 11 electoral districts. The 247 HC members serve six-year terms, with one-half of the members up for election every three years. Every three years, 48 HC members are elected from the nation at-large, and 73 are chosen from prefectural districts of varying size. The HR is responsible for the budget and other legislation, with the HC able to veto budgetary legislation approved in the HR, but the HR can override the veto. Two-thirds majorities in both houses are necessary to amend the Constitution.
Political turmoil characterizes Japanese politics since the Liberal Democratic Party's (LDP) disintegration in 1992 and its loss of parliamentary majority in the 1993 elections. In 1996, the LDP captured 239 seats with the now disbanded New Frontier Party garnering 156 seats. Since that time, the repeated exodus and return of party members kept the LDP's strength in a state of flux. The HC elections on 12 July 1998 resulted in the LDP's loss of 15 of 118 seats and prompted the resignation of Prime Minister Ryutaro Hashimoto. The Diet selected Keizo Obuchi to be the new prime minister of Japan, but he died in April 2000 after a stroke and coma. His successor, Yoshiro Mori, governed through a coalition with the Komeito Party and the Honshu-to, a new conservative party consisting of remaining Liberal Party members. This three-party coalition maintained its power following House of Representatives elections in June 2000. Mori's approval ratings fell sharply in the following year, however, and he agreed in April to hold House of Councillors elections in July 2001. In a surprise upset, "maverick" politician Junichiro Koizumi defeated former prime minister Ryutaro Hashimoto and other favored party members, promising a wave of political and economic reforms. On 26 April 2001, Koizumi became Japan's eighty-seventh prime minister.