Constitutional Democratic Party of Japan
The Constitutional Democratic Party of Japan is a liberal political party in Japan. It is the primary centre-left party in Japan, and was the second largest party in the National Diet behind the ruling [Liberal Democratic Party (Japan, 2016)|Democratic Party (Japan)|Liberal Democratic Party].
It was founded in October 2017 as a split from the Democratic Party ahead of the 2017 general election. In late 2020, the party was re-founded following a merger with majorities of the Democratic Party For the People and the Social Democratic Party as well as some independent lawmakers. In 2026, it announced its partial merger with Komeito to form the Centrist Reform Alliance.
The party's platform supports raising the minimum wage, expanded welfare policies, the legalization of same-sex marriage, increased gender equality, renewable energy policies, decentralization, a multilateral and pragmatic foreign policy, the revision of the U.S.–Japan Status of Forces Agreement, tax reform and electoral reform. The party strongly opposes efforts to amend the Japanese Constitution to reinterpret Article 9 or codify the status of the Japan Self-Defense Forces and also opposes nuclear power.
History
Formation and 2017 election
The party was formed in the run up to the 2017 general election from a split of the centre-left wing of the opposition Democratic Party. Prior to the election on 28 September 2017, the DP House of Representatives caucus dissolved in order for party members to stand as candidates for Tokyo governor Yuriko Koike's Party of Hope or as independents in the upcoming election.The new party was launched on 2 October 2017 by DP deputy leader Yukio Edano at a press conference in Tokyo for liberals and left-leaning members of the DP who did not wish to, or were rejected for, contesting the election as candidates for the Party of Hope.
On 3 October 2017, it was announced that the new party would not contest seats where former Democrats were running as Party of Hope candidates, a gesture which was not returned when the Party of Hope ran a candidate in Edano's incumbent district. The Japanese Communist Party, in turn, pulled their own candidate from running in Edano's district so as to not take away votes from him. The party won a total of 55 seats, becoming the leading opposition party and leading the pacifist bloc to become the largest opposition bloc.
In July 2020, the CDP became an observer affiliate of the Council of Asian Liberals and Democrats.
2020 merger and refoundation
On 19 August 2020, the CDP announced that it would merge with the majority of the Democratic Party For the People as well as some independent Diet members in September of that year.On 10 September 2020, the new party elected Edano as leader and voted to retain the CDP name. Following the merger, the new CDP had 149 members and held 107 seats in the House of Representatives, compared to 156 members and 96 seats held by the Democratic Party in 2016. The independents who joined the CDP in this merger included former Prime Minister Yoshihiko Noda. Several conservative DPP members, including DPP president Yuichiro Tamaki, did not join the CDP and instead continued to lead a rump DPP independent of the CDP.
On 14 November 2020, the Social Democratic Party voted to agree to a merger arrangement with the CDP, allowing SDP members to leave the party and join the CDP. SDP leader Mizuho Fukushima was opposed to the merger agreement and as a result remained in the Social Democratic Party.
The CDP contested the 2021 general election in an electoral pact co-operating with the JCP, Reiwa Shinsengumi and continuing DPP and SDP parties in fielding single opposition candidates in single-seat constituencies. Edano resigned as party leader following the election on 2 November 2021, due to poorer than expected electoral results, in which the CDP fell from 110 to 96 seats.
Kenta Izumi was elected as the leader of the CDP in the 2021 Constitutional Democratic Party of Japan leadership election on 30 November 2021. Formerly a member of the DPP, he said that the two parties are regarded by the public as "close" and "thought to be like brothers" and "expressed support for a tie-up" between the two.
On 23 September 2024, former Prime Minister Yoshihiko Noda was elected party president on the party leadership election, with Junya Ogawa chosen as party general secretary.
In the 2024 general election held on 27 October 2024, the CDP greatly increased their seat count in the House of Representatives to 148, depriving the ruling Liberal Democratic Party of their majority.
2026 merger with Komeito
On 15 January 2026, CDP president Noda announced that the party had agreed to merge with Komeito in the lower-house to form the Centrist Reform Alliance.Ideology and platform
The CDP has been described as liberal and social-liberal, and in favour of constitutionalism. The party has also been described as centre-left, progressive, and left-wing populist. Following its enlargement in 2020, the party has variously been described as liberal, centrist, or centre-left. Within the CDP, as with its predecessor the Democratic Party of Japan, there are conservative politicians, as well as politicians from social-democratic backgrounds.At launch in 2017, the CDP opposed the proposed revision of Article 9 of Japan's postwar constitution. The party supports the phasing out of nuclear energy in Japan, and government investment in renewable energy. The party does not support the legalization and maintenance of casinos. The party supports "building a society that supports each other and makes full use of individuality and creativity". In their 2017 political programme, the party expressed support for grassroots democracy and diplomatic pacifism.
In 2019, the party pledged to support LGBT rights and the legalization of same-sex marriage in Japan, and in March 2023, promoted a parliamentary bill for Japan to legally recognise such couplings.
The party supported a freeze in the increase of the consumption tax as of 2017, and supports a temporary consumption tax cut as of 2020, along with higher taxes on corporations and wealthy individuals. In the run-up to the 2021 general election, party leader Edano stated his party's support for redistribution of wealth. The 2021 election platform offered support for progressive taxation, a pledge for additional welfare payments for citizens on low incomes, and raising the capital gains tax rate to 25% by 2023.
The CDP's 2024 platform supported raising the minimum wage, the abolition of tuition fees, free school meals, gender equality legislation and reform of laws regulating use of surnames following marriage in Japan. The party also abandoned its previous policies of freezing or lowering the consumption tax rate.
The CDP released a statement on its official website in August 2025 in which it was stated that there was a need to recognize Palestine as an independent country.
Leadership
As of 23 January 2025. Only officials from the House of Councillors remain due to the formation of the Centrist Reform Alliance.| Position | Name | House |
| President | Shunichi Mizuoka | Councillors |
| Secretary-General | Jun Azumi | Councillors |
| Chairman of the Diet Affairs Committee | Yoshitaka Saitō | Councillors |
| Chairman of the Policy Reseach Council | Eri Tokunaga | Councillors |