Japanese Socialist Party
The Japanese Socialist Party was a social democratic party which was a major force in Japanese politics for much of the 20th century (insofar as any party was a major force beyond the ruling Liberal Democratic Party). In 1947 (when the Liberal and Democratic Parties ran separately), it won the largest number of seats in the lower house of Japan’s parliament, and won the second-largest number of seats there in every election between 1958 and 1993.
The JSP was founded in 1945, in part by activists who had been expelled from the Japanese Communist Party when it came under more direct influence by the Comintern during the late 1920s. On the other hand, other founders had been collaborators with Japan’s military regime during WW2. From the JSP’s beginning, there were two rival factions within the party: a left faction which identified with socialism and Marxism, and a right faction which did not. The party later split in 1951, a reflection of this ideological divide. But then they reunified later that decade, apparently.
The party somewhat reluctantly led a short-lived government after its election victory in 1947; it failed when it could not pass a budget (partly thanks to the conservative Liberal and Democratic Parties completely outnumbering it, but also because of the lack of cooperation from its own left faction). It then joined a coalition government which lasted only seven months before being brought down by a destructive leak from G-2 (the intelligence arm of the US occupation forces), alleging corruption on the part of the prime minister and other members of his government. After a 13-year trial the men were found to be innocent, but the damage was done to the reputations of their parties… The JSP lost two-thirds of its seats in the 1949 election.
The left faction regained in influence over the 1950s, in part thanks to the emergence of a new trade union federation, Sōhyō, over the ruins of the old trade union federation, Sanbetsu, which had been more radical but crushed by US-mandated “purge suspected communists” policies. The US occupation regime hoped that Sōhyō would remain strictly apolitical without its “communist” leaders, but the rank-and-file were still highly political (given they remembered being crushed by the repressive militaristic imperial regime, and saw Japanese rearmament and participation in the Korean War as a return to that situation) and the trade union federation, as a result, was left-wing.
In 1960 there was another split from the JSP, this time forming a new party called the Democratic Socialist Party, over the issue of the Anpo treaty with the US. Basically the DSP had a very moderate position on this treaty (which was deeply unpopular with left-wing voters in Japan) while the JSP wanted to break it. The DSP got between 6–8% of the vote in elections but never came close to eclipsing the JSP’s popularity, precisely because their point of differentiation was to take the unpopular position on a major political issue.
But then at the same time, the JSP began sliding away from worker-oriented politics to a more fuzzy, media-friendly politics full of soundbites but light on specific policies. Furthermore, corporations started offering more and more benefits to their employees as the Japanese economic boom got fully into swing, a phenomenon sometimes referred to as the “welfare company”. This weakened support for redistributive policies like those characterising a “welfare state”.
In 1966 the JSP adopted a really radical constitution predicated on the belief that Japanese capitalism was on the verge of imminent collapse. This was, of course, the result of more power struggles within the party, between the media-savvy “structural reform” people and the more traditional worker-oriented leftists (who nonetheless may have been a bit delusional about the status of Japanese capitalism). In a way this involved them switching places with their old rivals, the Communist Party, which had been the more radical historically but was now softening its own policy positions and reaching an accommodation with capitalism.
The JSP’s vote share gradually dropped over the 1970s and 80s, even though it remained the second-largest party in parliament. The largest party, the LDP, generally scored double the votes that it did. In 1986, they tried to stem the tide by dropping its 1966 constitution, but this did not work. Its vote share that year dropped to 17.2% – the LDP scored almost three times more. The JSP leadership had to resign. They got a new leader from a non-trade union background, Doi Takako, who somehow turned the party around such that they got 35.1% of the vote in the 1989 upper house elections (possibly related to her opposition to a consumption tax? idk), and 24% in the following year’s lower house elections. This didn’t last though, as the public gradually forgot their anger with the LDP over the consumption tax. Also, the JSP’s opposition to Japanese participation in UN peacekeeping missions was unpopular.
In 1994, the JSP agreed to enter into a coalition government with the LDP. Even though the LDP had like three times as many seats as them, it was a JSP politician who became prime minister. He immediately announced a complete about-face on many core JSP policies, like opposition to the US alliance, and opposition to militarism. JSP voters felt deeply betrayed and the party entered into a nosedive. The party renamed itself the Social Democratic Party in 1996, and in that year’s elections got only 6.4% of the vote and fifteen seats.
Over the time since 1996, the SDP has faded into near-irrelevance, barely clearing the 2% threshold to even get into parliament sometimes. Since 2020, when nearly all the party’s MPs were convinced to defect to a centrist party, they’ve only had one MP in parliament. In contrast, the Communist Party has actually had a lot more success in the post-Cold War era, including some of its best-ever electoral performances.