Why does Japan's social democratic party survive? An organizational perspective

This article asks what explains the survival of small parties by analyzing the survival of the Social Democratic Party of Japan (SDP). Many new parties were founded in the early 1990s but few have survived. The SDP is thus an outlier case. The SDP is a successor to the Japan Socialist Party (JSP) but many members of the JSP joined the new center-left Democratic Party of Japan (DPJ) in 1996. The DPJ prospered but the SDP has faded into electoral insignificance, barely maintaining enough support to qualify as a political party under Japanese law. How and why does the SDP survive despite its dismal performance in elections? I argue that the continuing support of the All Japan Prefectural and Municipal Workers Union (hereafter, Jichiro) has played a significant role in the SDP's survival. Jichiro officially decided to support the DPJ but some prefectural branches continued to support the SDP. The SDP case confirms that societal organizations have played a significant role more than charismatic leadership or policy distinctiveness for small party survival. The SDP case also indicates that societal organizations may hinder cooperation with other parties and might undermine unified opposition building against the Liberal Democratic Party (LDP).