Social Democratic Party (Japan)
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Social Democratic Party Japan
Social Democratic Party
Japanese nameShakai Minshu-t?
PresidentMizuho Fukushima
Founded19 January 1996; 25 years ago (1996-01-19)
Headquarters2-4-3-7F Nagata-cho, Chiyoda-ku, Tokyo 100-0014
IdeologySocial democracy[1]
Democratic socialism[2]
Political position
International affiliationSocialist International[7]
Colours  Sky blue[8]
House of Councillors[9]
House of Representatives
Prefectural assembly members[10]
Municipal assembly members[10]

The Social Democratic Party (, Shakai Minshu-t?, often abbreviated to Shamin-t?) is a political party in Japan that was established in 1996.[11] Since its reformation and name change in 1996, it has advocated pacifism and defined itself as a social-democratic party.[12] It was previously known as the Japan Socialist Party (, Nihon Shakait?, abbreviated to JSP in English).

The party was refounded in January 1996 by the majority of legislators of the former Socialist Party of Japan which was Japan's largest opposition party in the 1955 System. However, most of the legislators joined the Democratic Party of Japan after that. Five leftist legislators who did not join the SDP formed the New Socialist Party which lost all its seats in the following elections. The SDP enjoyed a short period of government participation from 1993 to 1994 as part of the Hosokawa cabinet and later formed a coalition government with the Liberal Democratic Party under 81st Prime Minister Tomiichi Murayama of the JSP from 1994 to January 1996. The SDP was part of ruling coalitions between January and November 1996 (First Hashimoto Cabinet) and from 2009 to 2010 (Hatoyama Cabinet).

In the 2019 Japanese House of Councillors election, the party won four representatives in the National Diet, two in the lower house and two in the upper house.

In November 2020 the party entered into a merger agreement with the Constitutional Democratic Party.[13]


Before 2000

In 1995, the former Japan Socialist Party (JSP) was in a deep crisis. Aiming at saving the party, the leadership of JSP decided to dissolve the party and to establish a new social democratic party. In January 1996, such a new party, the Social Democratic Party was established along with the dissolution of JSP. De jure, JSP changed its name to the Social Democratic Party (SDP) as an interim party for forming a new party. However, a movement for transforming the SDP into a new social-democratic and liberal party was unsuccessful. Under Murayama's successor Ry?tar? Hashimoto (LDP), the SDP remained part of the ruling coalition. Long before the disappointing result in the 1996 Japanese general election, the party lost the majority of its members of the House of Representatives, mainly to predecessors of the Democratic Party of Japan (DPJ) that was formed in 1996, but also some to the NFP and other opposition parties. After its electoral defeat in the 1996 general election when it lost another 15 of its remaining 30 seats in the lower house, the SDP left the ruling coalition which it had entered as the second largest force in Japanese politics as a minor party.


The SDP won six seats in the 2003 Japanese general election, compared with 18 seats in the previous 2000 Japanese general election. Its motives against the Self-Defense Forces have reverted into abolishing it in the long term, returning into its opposition against the force it had applied in the 1950s. Doi had been the leader since 1996, but she resigned in 2003, taking responsibility for the election losses. Mizuho Fukushima was elected as the new party leader in November 2003. In the 2004 Japanese House of Councillors election, the SDP won only two seats, having five seats in the House of Councillors and six seats in the House of Representatives. In 2006, the party unexpectedly gained the governorship of the Shiga Prefecture. In the 2009 Japanese general election, the DPJ made large gains and the SDP maintained its base of 7 seats in the, becoming a junior partner in a new government coalition. However, disagreements over the issue of the Futenma base led to the sacking of Fukushima from the cabinet on 28 May and the SDP subsequently voted to leave the ruling coalition.[14]

A SDP campaign van outside a station in December 2012

As of October 2010, the SDP had six members in the House of Representatives[15] and four members in the House of Councillors.[16] Following the 2012 Japanese general election, the party retained only six seats in the whole of the Diet, two in the House of Representatives and four in the House of Councillors. The count lowered to five seats in 2013. In 2013, the party's headquarters in Nagatacho, where the party's predecessor the JSP had moved in 1964, were demolished. The headquarters moved to a smaller office in Nagatacho.[17]

During the nomination period of the 2016 Japanese House of Councillors election, the party signed an agreement with the Democratic, Communist and People's Life parties to field a jointly-endorsed candidate in each of the 32 districts in which only one seat is contested, thereby uniting in an attempt to take control of the House from the LDP/Komeito coalition.[18] The party had two Councillors up for re-election and fielded a total of 11 candidates in the election, 4 in single and multi-member districts and 7 in the 48-seat national proportional representation block.[19]

In the 2017 Japanese general election, the party managed to hold to its two seats it had prior to the election. Tadatomo Yoshida declined to run for re-election when his term expired in January 2018. Seiji Mataichi was elected unopposed in the ensuing leadership election and took office on 25 February 2018.[20][21]

On 14 November 2020, the party voted to agree to a merger arrangement with the Constitutional Democratic Party (CDP), allowing members to leave the SDP and join the latter party. The majority of the party supported the agreement and thus joined the CDP. However, party leader Fukushima herself was opposed to the merger agreement and thus remains a member of the Social Democratic Party.[22]


Current party policies include:[12][23]


No. Name
Constituency / title Term of office Election results Photo (term)
Took office Left office
Preceding party: Japan Socialist Party (left-wing)
Chair of the Social Democratic Party (1996-present)
1 Tomiichi Murayama
Rep for
?ita 1st
19 January 1996 28 September 1996 - Tomiichi Murayama 19940630.jpg Hashimoto
(coalition, confidence and supply)
2 Takako Doi
Rep for
Hy?g? 7th
28 September 1996 15 November 2003 - Takako Doi in Tokyo congressist election 2.jpg
3 Mizuho Fukushima
Cou for
National PR
15 November 2003 25 July 2013 - Mizuho Fukushima.jpg
Abe S.
Fukuda Y.
Hatoyama Y.
(coalition until
30 May 2010)
Abe S.
- Seiji Mataichi

Cou for
National PR
(until 28 July 2019)
25 July 2013 14 October 2013 - Replace this image JA.svg
4 Tadatomo Yoshida
Cou for
National PR
(until 25 July 2016)
(29 July 2019 - present)
14 October 2013 25 February 2018
Tadatomo Yoshida - 9986
Taiga Ishikawa - 2239
Tadatomo Yoshida in SL Square in 2017.jpg
5 Seiji Mataichi
Cou for
National PR
(until 28 July 2019)
25 February 2018 22 February 2020
Replace this image JA.svg
6 Mizuho Fukushima
Cou for
National PR
22 February 2020 present
Mizuho Fukushima.jpg

Election results

General election results

Election Leader No. of
seats won
No. of
constituency votes
% of
constituency votes
No. of
PR block votes
% of
PR block votes
1996 Takako Doi
1,240,649 2.2 3,547,240 6.4 LDP-SDP-NPS coalition (1996-1998)
Opposition (1998-2000)
2000 Takako Doi
2,315,235 3.8 5,603,680 9.4 Opposition
2003 Takako Doi
1,708,672 2.9 3,027,390 5.1 Opposition
2005 Mizuho Fukushima
996,007 1.5 3,719,522 5.5 Opposition
2009 Mizuho Fukushima
1,376,739 2.0 3,006,160 4.3 DPJ-PNP-SDP coalition (2009-2010)
Opposition (2010-2012)
2012 Mizuho Fukushima
451,762 0.7 1,420,790 2.3 Opposition
2014 Tadatomo Yoshida
419,347 0.7 1,314,441 2.4 Opposition
2017 Tadatomo Yoshida
634,719 1.2 941,324 1.7 Opposition

Councillors election results

Election Leader No. of
seats total
No. of
seats won
No. of
National votes
% of
National vote
No. of
Prefectural votes
% of
Prefectural vote
1998 Takako Doi
4,370,763 7.8% 2,403,649 4.3%
2001 Takako Doi
3,628,635 6.63% 1,874,299 3.45%
2004 Mizuho Fukushima
2,990,665 5.35% 984,338 1.75%
2007 Mizuho Fukushima
2,634,713 4.47% 1,352,018 2.28%
2010 Mizuho Fukushima
2,242,735 3.84% 602,684 1.03%
2013 Mizuho Fukushima
1,255,235 2.36% 271,547 0.51%
2016 Tadatomo Yoshida
1,536,238 2.74% 289,899 0.51%
2019 Seiji Mataichi
1,046,011 2.09% 191,820 0.38%

Current Diet members

House of Representatives

House of Councillors

Up for re-election in 2022

See also


  1. ^ "Shakai Minshu-t? towa" [](?[]). (in Japanese). Retrieved 2020. (from Micropædia)
  2. ^ Donald F. Busky, ed. (2010). Democratic Socialism: A Global Survey. Greenwood Publishing Group. p. 201.
  3. ^ a b " , "?, ?"" (in Korean). IN. 24 April 2008. Retrieved 2020.
  4. ^ a b "?" (Press release). . 2006-02-11.
  5. ^ The Buraku Issue and Modern Japan: The Career of Matsumoto Jiichiro. Author - Ian Neary. P.67. Published by Routledge in London and New York in 2010.
  6. ^ Janet Hunter, Cornelia Storz, ed. (2006). Institutional and Technological Change in Japan's Economy: Past and Present. Routledge.
  7. ^ "Members". Socialist International. 29 May 2020.
  8. ^ [Will the colors of political parties settle in Japan?] (in Japanese). Nikkei, Inc. 21 October 2017. Retrieved 2020.
  9. ^ OfficialWeb. Social Democratic Party. Archived from the original on 21 July 2015. Retrieved 2015.
  10. ^ a b Ministry of Internal Affairs and Communications (30 March 2018). "Prefectural and municipal assembly members and chief executives by political party as of 31 December, 2017".
  11. ^ . National Diet Library. Archived from the original on 24 December 2014. Retrieved 2015.
  12. ^ a b "OfficialWebO". Social Democratic Party. Archived from the original on 31 July 2015. Retrieved 2015.
  13. ^ "Social Democratic Party to split; most Diet members to join CDPJ". The Japan Times. 25 February 2018. Retrieved 2020.
  14. ^ BBC News Socialists leave Japan coalition over Okinawa issue Archived 2010-11-03 at the Wayback Machine
  15. ^ "The House of Representatives". National Diet of Japan. Archived from the original on 22 March 2011. Retrieved 2017.
  16. ^ "List of the Members". National Diet of Japan. Archived from the original on 22 March 2011. Retrieved 2017.
  17. ^ Japan Times Japan's Social Democratic Party moving HQ out of historic Tokyo building January 27, 2013 Archived December 3, 2013, at the Wayback Machine
  18. ^ "Opposition parties, activists ink policy pact for Upper House election". Japan Times. 7 June 2016. Archived from the original on 9 June 2016. Retrieved 2016.
  19. ^ ?310 [Fewer candidates with the demise of the third pole - 10 celebrity candidates] (in Japanese). Yomiuri Shimbun. 23 June 2016. Retrieved 2016.
  20. ^ Takeshita, Yuka (26 January 2018). 2 (in Japanese). Asahi Shimbun. Archived from the original on 27 January 2018. Retrieved 2018.
  21. ^ (in Japanese). Nihon Keizai Shimbun. 25 February 2018. Archived from the original on 27 February 2018. Retrieved 2018.
  22. ^ "Social Democratic Party to split; most Diet members to join CDPJ". The Japan Times. 25 February 2018. Retrieved 2020.
  23. ^ OfficialWeb(). Archived from the original on 13 July 2015. Retrieved 2015.
  24. ^ Inada, Miho; Dvorak, Phred. "Same-Sex Marriage in Japan: A Long Way Away?" Archived 2016-06-16 at the Wayback Machine. The Wall Street Journal. September 20, 2013. Retrieved March 31, 2014.


External links

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