The was one of the main political parties in pre-war Empire of Japan. Commonly known as the Minseità Â, it was the main rival to the Rikken Seiyà «kai.
The party was founded in 1927 as a merger of Kenseikai and the Seiyà «hontà  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 Reijirà Â. The party strongly opposed the Mukden incident in 1931, leading Reijirà Â'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 Seiyà «kai. 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.
The Minseità  was founded on 1 June 1927, by a merger of the Kenseikai and the Seiyà «hontà  political parties. Its leadership included Hamaguchi Osachi, Wakatsuki Reijirà Â, Yamamoto Tatsuo, Takejirà  Tokonami, Adachi Kenzà Â, Koizumi Matajirà  and Saità  Takao. The party platform was politically and economically more liberal than its major rival, the Rikken Seiyà «kai, calling for rule by the Diet of Japan rather than bureaucrats or genrà Â, elimination of disparities in wealth, international cooperation, and protection of personal liberties.
The Minseità  fielded many candidates in the 1928 general election, (the first to be held after the General Election Law), winning 217 seats in the Lower House, as opposed to 218 seats for the Seiyà «kai. This resulted in a hung parliament. In the following 1930 general election, the Minseità  took 273 seats, as opposed to 174 seats for the Seiyà «kai, which gave it an absolute majority. Minseità  president Hamaguchi Osachi, Herbert Bix referred to him as Hamaguchi Yà «kà Â, became Prime Minister. Hamaguchi's first priority was to address the effects of the Wall Street crash of 1929 through retrenchment of government spending, tightening the money supply and encouraging exports while stabilizing foreign investments through returning to a fixed exchange rate. During its tenure, the Minseità  also advocated a conciliatory foreign policy and ratified the London Naval Agreement of 1930. However, Hamaguchi fell victim to assassination on 14 November 1930 when he was shot in Tokyo Station by a member of an ultranationalist secret society. Wakatsuki Reijirà  became acting Prime Minister, also from the Minseità Â.
In 1931, the Minseità  strongly opposed the Mukden incident which was engineered by the Imperial Japanese Army. The anti-war Foreign Minister Kijà «rà  Shidehara and Prime Minister Reijirà  came under strong criticism for their intervention in military affairs and were accused of "serious corruption", and his government collapsed in 1931. In the following 1932 general election, some right-wing members defected to the Rikken Seiyà «kai, which won an absolute majority of 301 seats. Seiyà «kai president Inukai Tsuyoshi became prime minister. The Minseità  was able to recover a very slight majority of 205 seats versus 175 seats for the Seiyà «kai in the 1936 general election only by adopting a more pro-military stance. However, the narrow margin again resulted in a hung parliament. The Minseità  dropped back down to 179 seats in the 1937 general election, while the Seiyà «kai retained all of its 175 seats, which continued the paralysis in the Diet of Japan. On 15 August 1940, the Minseità  voted to dissolve itself into the Imperial Rule Assistance Association as part of Fumimaro Konoe's efforts to create a one-party state, and thereafter ceased to exist.
The first article is a text that provides for the politics centered on the House of Representatives so it shows the superiority of the lower house over the upper house.
While both the Minseità  and their rivals Rikken Seiyà «kai advocated for a constitutional monarchy, the Minseità  held onto a more centrist, liberal and progressive platform than their conservative opposition the Seiyà «kai. The Minseità  was established as an anti-Seiyà «kai on 1 June 1927. However, the party was really more of a motley collection of politicians who wished to prevent the Seiyà «kai from taking power.
Under these circumstances, The Minseità  under the party's first president Hamaguchi. came to advocate 'liberty' and 'progress'. He defined the Minseità  as a progressive party that respected individual liberty and originality. In fact, over time, the Minseità  had grown into a progressive party aiming for freedom and equality in the course of fighting with the Seiyà «kai.
The Minseità  aimed to establish a two-party system, and the party has advocated . This is due to the influence of former members of the Kenseikai legislators who have gained experience as politicians of party politics, and it's an idea to oppose the Seiyà «kai which advocates Kà Âshitsu Chà «shinshugi (). Seigà  Nakano, the head of policymaking and public relations, declared that "The Minseità  will implement strong 'Parliament-centric politics' through good operation of the universal suffrage." The Minseità  was the first political party in Japan to self-styled the "Democratic Party."
The Minseità  was aimed at incremental democratization in cooperation with bureaucracy organization. Because this party had many party members who were once bureaucrats.
The headquarters of the Minseità  was in Sakurada-cho, Shiba-ku, Tokyo City. In 1947, Shiba-ku became the current Minato, Tokyo due to the merger with Akasaka-ku and Azabu-ku. Since the political parties at the time were not given corporate status, the land and building owners of the headquarters were not political parties. The owner of the Minseità  Headquarters was Minoura Katsundo, Onimaru Gisai. The party's newspaper was called Minsei.
The intraparty management of the Minseità  was autocracy by executives. The Minseità  legislators had almost monopolized the management positions and the political activities of the party were centered on legislators. The party rules stipulate that executives are publicly elected, but the party had become autocracy by executives because there was a motion at the convention that "It should be left to the president".
The Minseità  had professed that it had 2 or 3 million members, however leaders did not know the exact number of members. The party left the certificate for join/leave the party in the warehouse and did not neatly organize the membership list. Additionally, there were also many dual membership and floating members. For that reason, the exact number of the Minseità  is unknown.
Some members who not legislators had formed an organization called Ingaidan (). They essentially worked unpaid for campaigns, escorts, communications, anti-government movements, and election struggles. It's said that there were around 1,300 Ingaidan members in Tokyo Prefecture.
In the Minseità Â, factions called Kanryà Âha () and Tà Âjinha () were in conflict. Kanryà Âha members were at the center of the Minseità Â. They had an overwhelming ability to raise political funds because they were well-known in business community such as Mitsubishi zaibatsu. They also had a strong connections to genrà  and other privileged classes, so they had high policy-making ability. They were a collection of human resources that could rationalize administration, financial, and tax policies. One more faction, Tà Âjinha was rallying under Adachi Kenzà  who had a good reputation for astute skills in election campaign. Tà Âjinha members had many politicians who were active in the democratic movements. The younger age group of Tà Âjinha had a deep connection with a civil groups based on the middle class such as a youth political organization, and formed the left wing of the party that demanded executives to implement populist policies. However, a series of bankruptcies of local banks due to the financial crisis in the 1920s caused the decline of Tà Âjinhas a financial supporter, local business community. As a result, Tà Âjinha could not fully oppose Kanryà Âha.