One Party to Rule Them All? The Return of LDP Dominance to Japan

In 2009, the Liberal Democratic Party of Japan (LDP) lost in a landslide to the Democratic Party of Japan (DPJ), only the second time the LDP had lost since its formation in 1955. The culmination of dramatic changes to Japan’s institutions, party system, and demographics, this election seemed to portent a different future for Japan—one in which the LDP’s longtime dominance of Japanese politics was at an end. However, in 2012, the very next election, the DPJ splintered and the LDP managed to regain power. Between then and 2021, Japan’s opposition parties have grown weaker and the country’s party system has become lopsided again, with the LDP the lone large party running against several small parties. This project is concerned with understanding what has allowed LDP dominance to return to Japanese politics. The literature on Japanese politics has convincing theories on how the LDP won so consistently in the past, but the conditions that previously produced dominance have met with substantial changes over the past few decades. Scholars have yet to present a comprehensive case for why the LDP should dominate again under drastically different circumstances. Not only does my work speak to a central issue in Japanese politics, it provides insight into broader aspects of political science like party switching, the relative importance of candidate and party appeal to voters, and the relationship between party policy and valence on voter choice. I tackle the question of the return LDP dominance with a three-pronged approach. First, I study what contributed to the DPJ’s collapse. LDP dominance would arguably be far less likely if the DPJ had managed to avoid splitting apart in 2012, making this election a natural starting point for analyzing the LDP’s return. I find that party switching among DPJ members was driven by a combination of how well candidates did under the DPJ in the previous election and the candidates’ policy preferences. Candidates that had lower vote shares or policy preferences further from the median DPJ preference were more likely to switch parties, and the parties to which they switched had preferences closer to their own. In other words, the DPJ was split apart by candidates looking for a better fit to boost their chances in the upcoming election, implying that party affiliation was a crucial part of candidates’ calculus of political competition. Second, building off the implications from the first analysis, I examine how important party competition is in Japan since the DPJ’s debacle in 2012. In years past, the LDP’s strength has come from a combination of cash, clientelistic networks, and strong candidates, but recent research has found that Japanese politics has become more programmatic and party-focused. Here I find that while LDP dominance since its return to power in 2012 can be attributed in part to its candidates, the appeal of the party label has played a substantial role in securing the LDP’s large majorities. Party affiliation continues to define electoral competition in Japan despite the loss of the DPJ as a clear alternative to the LDP. Third, given that parties remain important in Japanese elections, I examine what exactly about the LDP appeals to voters. Drawing from the literature valence, which highlights the significance of things like competence and capability on voter choice, I provide evidence that the LDP lost in 2009 due to poor policy positioning while facing the DPJ, a party with comparable valence. However, after the DPJ split apart, the LDP was able to dominate the fragmented parties with their much lower valence. I conclude that opposition parties in Japan are either poorly positioned on policy relative to voter preferences or do not have the necessary valence to compete with the LDP even when better positioned on policy. My research tells the story of a party that now dominates through its party brand in a political system that emphasizes party competition, a sharp contrast from the candidate-centered politics that cemented the LDP’s dominant legacy in the past. The larger implications from this work are that, despite the LDP’s return to power, Japan has responded to underlying changes in its politics. Furthermore, while the LDP dominates today, its position as a dominant party is likely far weaker than it was under the previous era of dominance. Japanese politics have become nationalized, policy-based, and party-focused and these conditions are much more susceptible to party system change than the robust, candidate-controlled clientelism that kept the LDP in power for decades