Constitutional Democratic Party (Japan)

The Constitutional Democratic Party (Japanese: 立憲民政党, Hepburn: Rikken Minseitō) was one of the main political parties in pre-war Empire of Japan. Commonly known as the Minseitō, it was the main rival to the Rikken Seiyūkai.

The party was founded in 1927 as a merger of Kenseikai and the Seiyūhontō political parties. It won 217 seats in the 1928 general election, resulting in a hung parliament. In the 1930 general election, the party won an absolute majority with 174 seats, leading its president Hamaguchi Osachi to become the Prime Minister of Japan. Focusing on economic recovery following the Wall Street crash of 1929 , Hamaguchi was assasinated in 1930, leading him to be succeeded by Wakatsuki Reijirō. The party strongly opposed the Mukden incident in 1931, leading Reijirō's government to collapse that year.

The party lost a significant amount of seats in the 1932 general election, which saw the election of Rikken Seiyūkai. It adopted a pro-military stance afterwards, and won a slight plurality of 205 seats in the 1936 general election, resulting in a hung parliament. In the 1937 general election, it dropped to 179 seats, which continued the paralysis in the parliament. In 1940, the party voted to merge itself to the Imperial Rule Assistance Association, which became the sole ruling party of Japan until 1945.