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Constitutional Democratic Party of Japan

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Constitutional Democratic Party of Japan

The Constitutional Democratic Party of Japan (立憲民主党, Rikken-minshutō; CDP or CDPJ) 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 (LDP). It was founded in October 2017 as a split from the Democratic Party ahead of the 2017 general election, where it allied with the Japanese Communist Party and Social Democratic Party and overtook Kibō no Tō to become the largest opposition party. 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 the 2021 general election, it underperformed expectations and lost several seats. In the 2024 general election, the party surged and achieved the best result in its history, gaining 148 seats, up from 96 before. In 2026, it merged with Komeito in the House of Representatives to form the Centrist Reform Alliance in advance of the 2026 general election, however the party still caucuses as the CDP in the House of Councillors and in local elections. In the 2026 election, CDP-affiliated members of the CRA lost most of their seats, reducing the number of CDP-affiliated representatives from 144 to 21. 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 .–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.

Infobox

Abbreviation
CDP CDPJ
President
Shunichi Mizuoka
Secretary-General
Masayo Tanabu
Founder
Yukio Edano
Founded
3 October 2017 (2017-10-03) 15 September 2020 (2020-09-15)
Split from
Democratic Party (2016)
Preceded by
Constitutional Democratic Party of Japan
Merged into
Centrist Reform Alliance (House of Representatives)
Headquarters
2-12-4 Fuji Building 3F, Hirakawa-chō, Chiyoda-ku, Tokyo 102-0093, Japan
Newspaper
Rikken-minshu
Youth wing
RikkenYouth
Membership (August 2024)
114,839
Ideology
Liberalism (Japanese) Social liberalism
Political position
Centre to centre-left
National affiliation
Centrist Reform Alliance (2026–present)
International affiliation
Council of Asian Liberals and Democrats (observer)
Colors
Blue
Slogan
政権交代こそ、最大の政治改革。 Seiken koutai koso, saidaino seijikaikaku. ('A change of government is the biggest political reform.')
Councillors
39 / 248
Representatives
0 / 465
Prefectural assembly members
231 / 2,614
Municipal assembly members
730 / 28,940

Tables

· Leadership › Current leadership
Shunichi Mizuoka
Shunichi Mizuoka
Position
President
Name
Shunichi Mizuoka
Masayo Tanabu
Masayo Tanabu
Position
Secretary-General
Name
Masayo Tanabu
Tadatomo Yoshida
Tadatomo Yoshida
Position
Chairman of the Standing Committee
Name
Tadatomo Yoshida
Yoshitaka Saitō
Yoshitaka Saitō
Position
Chairman of the Diet Affairs Committee
Name
Yoshitaka Saitō
Shinji Morimoto
Shinji Morimoto
Position
Chairman of the Election Strategy Committee
Name
Shinji Morimoto
Eri Tokunaga
Eri Tokunaga
Position
Chairman of the Policy Research Council
Name
Eri Tokunaga
Position
Name
President
Shunichi Mizuoka
Chairman in the House of Councillors
Secretary-General
Masayo Tanabu
Chairman of the Standing Committee
Tadatomo Yoshida
Chairman of the Diet Affairs Committee
Yoshitaka Saitō
Chairman of the Election Strategy Committee
Shinji Morimoto
Chairman of the Policy Research Council
Eri Tokunaga
· Leadership › List of leaders
Split from: Democratic Party (2016) (centre-left)
Split from: Democratic Party (2016) (centre-left)
No.
Split from: Democratic Party (2016) (centre-left)
1
1
No.
1
Leader (birth–death)
Yukio Edano (b. 1964)
Leader (birth–death)
Constituency
Rep for Saitama 5th
Took office
3 October 2017
Left office
14 September 2020
Election results
2017 Unopposed
Merger of: Democratic Party For the People (centre-right; majority faction) & Some Independents Group
Merger of: Democratic Party For the People (centre-right; majority faction) & Some Independents Group
No.
Merger of: Democratic Party For the People (centre-right; majority faction) & Some Independents Group
1
1
No.
1
Leader (birth–death)
Yukio Edano (b. 1964)
Leader (birth–death)
Constituency
Rep for Saitama 5th
Took office
15 September 2020
Left office
12 November 2021
Election results
2020 Yukio Edano – 107 Kenta Izumi – 42
2
2
No.
2
Leader (birth–death)
Kenta Izumi (b. 1974)
Leader (birth–death)
Constituency
Rep for Kyoto 3rd
Took office
30 November 2021
Left office
23 September 2024
Election results
2021 1st Round Kenta Izumi – 189 Seiji Osaka – 148 Junya Ogawa – 133 Chinami Nishimura – 102 2021 2nd Round Kenta Izumi – 205 Seiji Osaka – 128
3
3
No.
3
Leader (birth–death)
Yoshihiko Noda (b. 1957)
Leader (birth–death)
Constituency
Rep for Chiba 4th
Took office
23 September 2024
Left office
19 January 2026
Election results
2024 1st Round Yoshihiko Noda – 267 Yukio Edano – 206 Kenta Izumi – 143 Harumi Yoshida – 122 2024 2nd Round Yoshihiko Noda – 232 Yukio Edano – 180
4
4
No.
4
Leader (birth–death)
Shunichi Mizuoka (b. 1956)
Leader (birth–death)
Constituency
Councillor for National PR
Took office
23 January 2026
Left office
Incumbent
No.
Leader (birth–death)
Constituency
Took office
Left office
Election results
Split from: Democratic Party (2016) (centre-left)
1
Yukio Edano (b. 1964)
Rep for Saitama 5th
3 October 2017
14 September 2020
2017 Unopposed
Merger of: Democratic Party For the People (centre-right; majority faction) & Some Independents Group
1
Yukio Edano (b. 1964)
Rep for Saitama 5th
15 September 2020
12 November 2021
2020 Yukio Edano – 107 Kenta Izumi – 42
2
Kenta Izumi (b. 1974)
Rep for Kyoto 3rd
30 November 2021
23 September 2024
2021 1st Round Kenta Izumi – 189 Seiji Osaka – 148 Junya Ogawa – 133 Chinami Nishimura – 102 2021 2nd Round Kenta Izumi – 205 Seiji Osaka – 128
3
Yoshihiko Noda (b. 1957)
Rep for Chiba 4th
23 September 2024
19 January 2026
2024 1st Round Yoshihiko Noda – 267 Yukio Edano – 206 Kenta Izumi – 143 Harumi Yoshida – 122 2024 2nd Round Yoshihiko Noda – 232 Yukio Edano – 180
House of Representatives group merges into Centrist Reform Alliance
4
Shunichi Mizuoka (b. 1956)
Councillor for National PR
23 January 2026
Incumbent
House of Representatives · Election results › House of Representatives
No.
No.
Election
No.
Leader
±
No. of candidates
Share
Seats
No.
Seats
Share
Seats
No.
Position
Share
2017
2017
Election
2017
Leader
Yukio Edano
No. of candidates
78
Seats
55 / 465
Seats
11 %
Position
2nd
Constituency votes
4,852,097
Constituency votes
8 %
PR Block votes
11,084,890
PR Block votes
19 %
Status
Opposition
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
Election
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
2021
2021
Election
2021
Leader
Yukio Edano
No. of candidates
240
Seats
96 / 465
Seats
20 %
Position
2nd
Constituency votes
17,215,621
Constituency votes
29 %
PR Block votes
11,492,095
PR Block votes
20 %
Status
Opposition
2024
2024
Election
2024
Leader
Yoshihiko Noda
No. of candidates
237
Seats
148 / 465
Seats
52
Seats
31 %
Position
2nd
Constituency votes
15,740,860
Constituency votes
29 %
PR Block votes
11,564,217
PR Block votes
21 %
Status
Opposition
Merger with Komeito, forming the Centrist Reform Alliance (2026)
Merger with Komeito, forming the Centrist Reform Alliance (2026)
Election
Merger with Komeito, forming the Centrist Reform Alliance (2026)
Election
Leader
No. of candidates
Seats
Position
Constituency votes
PR Block votes
Status
No.
±
Share
No.
Share
No.
Share
2017
Yukio Edano
78
55 / 465
11 %
2nd
4,852,097
8 %
11,084,890
19 %
Opposition
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
2021
Yukio Edano
240
96 / 465
20 %
2nd
17,215,621
29 %
11,492,095
20 %
Opposition
2024
Yoshihiko Noda
237
148 / 465
52
31 %
2nd
15,740,860
29 %
11,564,217
21 %
Opposition
Merger with Komeito, forming the Centrist Reform Alliance (2026)
House of Councillors · Election results › House of Councillors
Won
Won
Election
Won
Leader
±
No. of candidates
Total
Seats
±
Seats
No.
Seats
Share
Seats
No.
Position
Share
2019
2019
Election
2019
Leader
Yukio Edano
No. of candidates
42
Seats
17 / 124
Seats
32 / 245
Position
2nd
Constituency votes
7,951,430
Constituency votes
15 %
Party list votes
7,917,720
Party list votes
15 %
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
Election
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
2022
2022
Election
2022
Leader
Kenta Izumi
No. of candidates
51
Seats
17 / 125
Seats
39 / 248
Position
2nd
Constituency votes
8,154,330
Constituency votes
15 %
Party list votes
6,771,914
Party list votes
12 %
2025
2025
Election
2025
Leader
Yoshihiko Noda
No. of candidates
51
Seats
22 / 125
Seats
5
Seats
38 / 248
Seats
1
Position
2nd
Constituency votes
9,119,656
Constituency votes
15 %
Party list votes
7,397,456
Party list votes
12 %
Election
Leader
No. of candidates
Seats
Position
Constituency votes
Party list votes
Status
Won
±
Total
±
No.
Share
No.
Share
2019
Yukio Edano
42
17 / 124
32 / 245
2nd
7,951,430
15 %
7,917,720
15 %
Merger of: Democratic Party For the People (centre-right; majority faction) & some Independents (2020)
2022
Kenta Izumi
51
17 / 125
39 / 248
2nd
8,154,330
15 %
6,771,914
12 %
2025
Yoshihiko Noda
51
22 / 125
5
38 / 248
1
2nd
9,119,656
15 %
7,397,456
12 %

References

  1. Interim leader, as registered with the Minister for Internal Affairs and Communications.
  2. The "old CDP" was founded on 3 October 2017 as a split from the Democratic Party and dissolved on 14 September 2020, whi
  3. Most conservative factions within the CDP are moderate conservatives, but some CDP members belong to ultra-conservative
  4. Held after the merger with the Democratic Party For the People.
  5. The Upper house is split in two classes, one elected every three years.
  6. Ministry of Internal Affairs and Communications
    https://www.soumu.go.jp/main_content/000511048.pdf
  7. Ministry of Internal Affairs and Communications
    https://www.soumu.go.jp/main_content/000706849.pdf
  8. Ministry of Internal Affairs and Communications
    https://www.soumu.go.jp/main_content/000706856.pdf
  9. cdp-japan
    https://cdp-japan.jp/form/party-organ
  10. cdp-japan
    https://cdp-japan.jp/rikken-youth
  11. "立民代表選、党員・協力党員11万人に投票権 合計740ポイントの争奪戦に"
    https://www.sankei.com/article/20240826-O6QD6XOIORNVHO2VEXHTIPDICQ/
  12. 日本経済新聞
    https://r.nikkei.com/article/DGXMZO22461210Z11C17A0000000
  13. "政党のキャッチフレーズからみえる戦略、有権者の心をつかむ言葉は?"
    https://www.yomiuri.co.jp/election/shugiin/20241019-OYT1T50090/
  14. Ministry of Internal Affairs and Communications, party membership statistics for chief executives and assembly members i
    http://www.soumu.go.jp/senkyo/senkyo_s/data/syozoku/ichiran.html
  15. The Japan Times
    https://www.japantimes.co.jp/news/2021/10/16/national/politics-diplomacy/ldp-nervous-opposition/
  16. Reuters
    https://www.reuters.com/world/us/heads-japan-major-parties-hold-debate-ahead-key-election-2021-10-18/
  17. The State and Politics of Japan (2nd ed.)
    https://books.google.com/books?id=64-ZDwAAQBAJ&pg=PT106
  18. "New centre-left party launched in Japan ahead of vote"
    https://web.archive.org/web/20171002220058/http://www.channelnewsasia.com/news/asiapacific/new-centre-left-party-launched-in-japan-ahead-of-vote-9271376
  19. Historical Dictionary of Postwar Japan
    https://books.google.com/books?id=jyx1DwAAQBAJ&pg=PA61
  20. The Yomiuri Shimbun
    https://web.archive.org/web/20171002215742/http://the-japan-news.com/news/article/0003978833
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