In this contribution, I use the breakup – just short of the 2017 General Election – of Japan’s former second biggest political party, the Democratic Party of Japan (DPJ), as a case study so as to assess the practical implications of splits and realignments in the most relevant party split in Japan since the DPJ was ousted from government in 2012. First, I examine DPJ’s origin as an umbrella for ideologically diverse groups that opposed the conservative Liberal Democratic Party (LDP) – the government party in Japan throughout most of its post-war history, its tendency to factionalism, and the oftentimes damaging role the factional dynamics played in the party’s decision-making process throughout the years. In the case study, it is understood that the creation of the Party of Hope – a split from the LDP, and the salience of constitutional issues were exogenous factors particular to that election, which helped causing the DPJ split.