The Socialist and Communist Joint Struggle (社共共闘, Shakyō kyōtō) refers to the political strategy in which the Japan Socialist Party (JSP; now the Social Democratic Party) and the Japanese Communist Party (JCP) fielded unified candidates and cooperated in elections.

Overview It became particularly active from the late 1960s, mainly in mayoral elections. It was also more broadly referred to as the "progressive joint struggle" (kakushin kyōtō).

The Democratic Socialist Party (DSP), formed in January 1960 by Diet members who left the JSP, had from the outset advocated anti-communism and rarely cooperated in opposition joint struggles. In the February 1967 Kitakyushu mayoral election, the same month's Kyoto mayoral election, the April 1967 Tokyo gubernatorial election, and the same month's Fukuoka gubernatorial election, the DSP supported unified candidates with the Liberal Democratic Party (LDP). On 22 February of that year, JSP Chairman Kōzō Sasaki stated that "the DSP is a second conservative party," and at an expanded central committee meeting on 5 March he further sharply criticized that "DSP leaders are helping the LDP's efforts to divide the opposition."Chūnichi Shimbun, morning edition, 6 March 1967, 11th edition, page 1, "Sasaki JSP Chairman Criticizes DSP Again". Of these, the JSP–JCP unified candidates won the Kyoto mayoral and Tokyo gubernatorial elections, but they lost by narrow margins in the 1971 Aichi gubernatorial election, the 1975 and 1979 Hokkaido gubernatorial elections, the 1975 Tachikawa mayoral election, and the same year's Higashikurume mayoral election to LDP–DSP unified candidates.

The nationwide trend of Socialist–Communist joint struggle continued until the late 1970s. After defeats in the two major elections of April 1979—the Hokkaido gubernatorial election and the 1979 Tokyo gubernatorial election—it subsided from the 1980s onward.

1950s 1950 April – The Kyoto gubernatorial election involved joint struggle. Torazō Ninagawa, the JSP-endorsed candidate, ran with the recommendation of the All-Kyoto Democratic Front Unification Conference, which included the JCP. He defeated Seiichi Inoue, who was recommended by the Democratic Liberal Party and the Japan Democratic Party, in a one-on-one contest and was elected for the first time. (Joint struggle, Elected)

1958 July – The Itō mayoral election involved joint struggle. Motokazu Numata, a representative of the Itō Credit Association, ran with the recommendations of the JSP and JCP. He defeated Miyomatsu Maeda, the LDP-endorsed candidate, in a one-on-one contest and was elected for the first time. (Joint struggle, Elected)

1959 April – The 1959 Hokkaido gubernatorial election was a de facto joint struggle. Setsuji Yokomichi, a member of the House of Representatives from Hokkaido 1st district, ran as the JSP-endorsed candidate. Because Yokomichi's spouse's elder brother was former Central Committee Chairman Eitarō Noro, the JCP provided rear support. Kingo Machimura, also a House of Representatives member from the same Hokkaido 1st district, ran as the LDP-endorsed candidate and defeated Yokomichi and others, winning for the first time. This marked the first postwar conservative prefectural government in Hokkaido. (Joint struggle, Defeated)

1960s

1960 24 January – The founding convention of the Democratic Socialist Party was held at Kudan Kaikan. Diet members who left the JSP to join the DSP numbered 38 in the House of Representatives and 16 in the House of Councillors.Chūbu Nihon Shimbun, evening edition, 24 January 1960, page 1, "Democratic Socialist Party Launched". September – The Fukuoka mayoral election involved joint struggle. Former House of Representatives member Shōko Fukuda ran with the JSP's recommendation and JCP support but was defeated by former Home Ministry bureaucrat Katsuji Sugimoto, recommended by the LDP and DSP. (Joint struggle, Defeated)

1962 July – The Itō mayoral election involved joint struggle. Incumbent Motokazu Numata ran with the recommendations of the JSP and JCP. He defeated LDP-endorsed Kuniemon Iijima in a one-on-one contest and was re-elected. (Joint struggle, Elected)

1963 March – The Kitakyushu mayoral election involved joint struggle. Former House of Councillors member Hōsei Yoshida ran as the JSP-endorsed candidate with the JCP's recommendation. He defeated Katsuji Sugimoto, recommended by the LDP and DSP, in a one-on-one contest and was elected for the first time. (Joint struggle, Elected)

April – The 1963 Tokyo gubernatorial election involved joint struggle. Masaru Sakamoto ran with the recommendations of the JSP, JCP, and DSP but was defeated by incumbent Ryūtarō Azuma, recommended by the LDP. (Joint struggle, Defeated)

April – The Kawasaki mayoral election saw a split. Former House of Representatives member Hideo Nakajima ran with the JSP's recommendation, while Takeo Konno ran as the JCP-endorsed candidate. Votes were split, and incumbent Fujitarō Kanasashi, recommended by the LDP, won a fifth term (Kanasashi: 141,979 votes; Nakajima: 134,588 votes; Konno: 18,989 votes). (Split, Defeated)

1965 April – The Nagoya mayoral election involved joint struggle. Former House of Councillors member Shin'ichi Kondō ran as the JSP-endorsed candidate with the JCP's recommendation but was defeated by incumbent Kiyoshi Sugito, recommended by the LDP and DSP. (Joint struggle, Defeated)

1966 October – The Goshogawara mayoral election involved joint struggle. Former mayor Hisaburō Yamauchi ran with the recommendations of the JSP and JCP but was defeated by incumbent Eizō Sasaki, LDP-endorsed. (Joint struggle, Defeated)

November – The Yamagata mayoral election involved joint struggle. Former prefectural assembly member Tadao Kanazawa ran as the JSP-endorsed candidate with the JCP's recommendation. He defeated independent conservative Hiroshi Mogi and LDP-endorsed Takeshi Yamamoto and was elected for the first time. (Joint struggle, Elected)

1967 January – The Ehime gubernatorial election involved joint struggle. Isamu Yuyama ran with the recommendations of the JSP and JCP but was defeated by incumbent Sadamu Hisamatsu, LDP-endorsed. (Joint struggle, Defeated)

January – The Kōchi mayoral election involved joint struggle. Former House of Councillors member Akira Sakamoto ran as the JSP-endorsed candidate with the JCP's recommendation. He defeated LDP-recommended Mangio Hiromatsu in a one-on-one contest and was elected for the first time. (Joint struggle . Elected)

February – The Esashi mayoral election saw a split. Kikuzō Satō ran with the recommendations of the JSP and DSP, while Kazuo Konno ran as the JCP-endorsed candidate. Satō defeated incumbent Nagazumi Watanabe and was elected for the first time. (Split)

22 February – JSP Chairman Kōzō Sasaki visited Kyoto to support newcomer Kiyoshi Tomii, the JSP–JCP-recommended candidate in the Kyoto mayoral election, and stated at a press conference that "the DSP is a second conservative party." The DSP reacted furiously; upon hearing this, party Secretary-General Eiichi Nishimura retorted, "How dare they insult our party. The JSP is a second Communist Party."Fumio Miyamura, "Scholars' War in the Tokyo Gubernatorial Election", Keizai Ōrai, April 1967 issue, Keizai Ōraisha, pp. 155–167.

23 February – The Kitakyushu mayoral election saw a split. Incumbent Hōsei Yoshida ran as the JSP-endorsed candidate, while Hiroyuki Tadakuma ran with the JCP's recommendation, splitting the vote. Gohei Tani, recommended by the LDP and DSP, was elected for the first time. (Split . Defeated)

26 February – The Kyoto mayoral election involved joint struggle. JSP–JCP-recommended Kiyoshi Tomii defeated LDP–DSP-recommended Masafumi Yasugi in a one-on-one contest and was elected for the first time. (Joint struggle . Elected)

April – The 1967 Tokyo gubernatorial election involved joint struggle. Economist Ryokichi Minobe ran with the recommendations of the JSP and JCP. He defeated Masatoshi Matsushita, recommended by the DSP and LDP, and others, and was elected for the first time. (Joint struggle . Elected)

April – The Kanagawa gubernatorial election saw a split. Former prefectural assembly member Shirō Takeda ran as the JSP-endorsed candidate, while Shuntarō Watanabe ran as the JCP-endorsed candidate, splitting the vote. Bungo Tsuda, recommended by the LDP, was elected for the first time. (Split . Defeated)

April – The Fukuoka gubernatorial election involved joint struggle. Incumbent Taichi Uzaki ran as the JSP-endorsed candidate with the JCP's recommendation but was defeated by Hikaru Kamei, recommended by the LDP and DSP. (Joint struggle . Defeated)

April – The Utsunomiya mayoral election saw a split. JSP-recommended Daihachi Ōnuki and JCP-endorsed Teiichi Kobanawa ran. They were defeated by former prefectural assembly member Yoshiko Koike (male), who ran as the LDP-endorsed candidate.. (Split . Defeated)

April – The Kunitachi mayoral election involved joint struggle. Nippon Express employee Kazuo Ishizuka ran as the JSP-endorsed candidate with the JCP's recommendation. He defeated two conservative candidates, Sagenza Sawao and Isao Wada, and was elected for the first time. (Joint struggle . Elected)

April – The Kawasaki mayoral election saw a split. Teruji Yoshihama ran as the JSP-endorsed candidate, Takeo Konno as the JCP-endorsed candidate, and Yoshiro Kasai as the DSP-endorsed candidate. Votes were split, and incumbent Fujitarō Kanasashi, recommended by the LDP, won a sixth term. (Split . Defeated)

April – The Hirakata mayoral election involved joint struggle. Tomizō Yamamura ran as the JSP-endorsed candidate with the JCP's recommendation. Incumbent Sōichirō Terashima, a former JSP member, ran with the recommendations of the LDP and DSP. Yamamura defeated Terashima and others and was elected for the first time. (Joint struggle . Elected)

April – The Takamatsu mayoral election saw a split. Nobuo Waki ran as the JSP-endorsed candidate and Yukio Shimokawa as the JCP-endorsed candidate. Votes were split, and LDP-endorsed Tokusaburō Miyake was elected for the first time. (Split . Defeated)

October – The Hōya mayoral election involved joint struggle. Akitoshi Harada ran as the JSP-endorsed candidate with the JCP's recommendation and was elected unopposed for the first time. (Joint struggle . Elected)

1968 February – The Fujisawa mayoral election saw a split. Former city assembly member Shun Hayama ran with the JSP's recommendation, while Kan Abe ran as the JCP-endorsed candidate, splitting the vote. Incumbent Koichirō Kaneko was elected. (Split . Defeated)

June – The Saitama gubernatorial election involved joint struggle. Yutaka Awaya ran with the recommendations of the JSP, JCP, and DSP but was defeated by incumbent Hiroshi Kurihara, LDP-endorsed. (Joint struggle . Defeated)

November – The 1st Chief Executive of the Ryukyu Government election involved joint struggle. Educator Chōbyō Yara ran with the support of the JSP, JCP, Okinawa Social Mass Party, and others. He defeated Junji Nishime, endorsed by the Okinawa Liberal Democratic Party, in a de facto one-on-one contest and was elected for the first time. (Joint struggle . Elected)

1969 January – The Hōya mayoral election saw a split. In the election following Mayor Harada's resignation over a corruption scandal, Tetsuya Tomaru ran as the JSP-endorsed candidate and Hiroshi Ōnami as the JCP-endorsed candidate. LDP-recommended Toshinori Naitō pulled ahead and was elected for the first time. (Split . Defeated)

February – The Matsumoto mayoral election involved joint struggle. Matsumi Fukazawa ran with the recommendations of the JSP, JCP, and DSP. He defeated incumbent Tokuya Furuhata, LDP-endorsed, in a one-on-one contest and was elected for the first time. (Joint struggle . Elected)