The following is my response to a comment from Ross to my previous post:If the DPJ wins the two-thirds supermajority required to override an Upper House (HC; House of Councilors) veto, this game is over. The DPJ has the public and constitutional mandate to have their way in the Diet. It will surely welcome any Lower House (HR; House of Representatives) members representing single-seat district defecting from the LDP. But since it does not need collaborators to govern, it will not provide few incentives if any. Moreover, the LDP survivors will be a hardy bunch, better able to resist the temptation to “better sidle up to a big tree under its shadow” and wait for the next HR general election under a new generation of policy-savvy leaders. Ideologically, they will continue to comprise a motley crew, but will look no worse in that respect than the DPJ. There is little likelihood of a post-election realignment that splits the LDP under this scenario.
If the DPJ manages to gain an HR majority but falls short of the two-thirds supermajority, it must achieve a working majority in the HC in order to carry out its policy agenda. (An HR caucus that creates a supermajority will have the same effect, but that outcome came be dealt with mostly as a variation of this scenario.) This requires a minimum of 121 out of the effective 240 votes. (The HC has 242 seats but its nominally independent President and Vice-President hail from the DPJ and LDP respectively so it is effectively a 240-seat chamber.) The DPJ-People’s New Party (PNP)-New Party Nippon (NPN) caucus has 118 members. The Social Democratic Party (SDP)-Pro-Constitution Alliance caucus has five seats, which would put the DPJ-led coalition comfortably over the top in the HC. That is surely why Ichiro Ozawa has squashed internal dissent to refrain from fielding DPJ HR candidates in 11 single-seat districts and support SDP candidates instead. (Note that the DPJ is being more generous to the SDP than its formal HC caucus partners—the PNP has eight similarly-favored candidates and the NPN has only one.) However, the SDP clear stands to the left of the DPJ and its other prospective coalition partners, which could become a serious constraint on the DPJ as it tries to govern from the reformist middle.
There are three true HC independents, that is, legislators other than House President and Vice-Presidents who do not formally caucus with any party; Naoki Tanaka, Ryuhei Kawada and Keiko Itokazu. If the DPJ can cut deals with all three, it will have a working majority of 121 votes. Tanaka, a recent LDP defector, is likely in the bag since his wife Makiko already caucuses with the DPJ. Kawada is close to Yasuo Tanaka, the NPN. He has a human-rights agenda, but the DPJ should be able to subsume it without much of a hitch. Itokazu is a leader of a Okinawa regionalist party to the left of the political spectrum who was elected with the support of the DPJ, SDP and the Japan Communist Party (JCP). As such, she is likely to vote with the coalition most of the time but side with the SDP (and likely aligning herself with the JCP as well) when it dissents.
Our look at the prospective coalition partners and the HC independents suggests that a coalition government led by a DPJ that lacks an HR supermajority is workable but is likely to be constrained by the need to keep a small band of leftists on board. Thus, the DPJ will be sorely tempted to lure LDP defectors, mainly in the HR, to its fold with offers of plum political assignments. Mass defection from the LDP is not out of the question but the DPJ is likely to prefer a small number of transfers that gives them a comfortable majority in the HC.
Things get really dicey if the DPJ wins more HR seats than the LDP-New Komeito coalition but falls short of a majority. (Or the other way around for that matter.) Much will depend on the composition of the remainder of the HR, but it is clear that that the inherent instability of any such situation will be deeply unsettling to the status quo in both major parties. Anything from a grand coalition to a fragmentation of the LDP is possible. If the margin is narrow, announcement of a few quick LDP defectors in both Houses could seal the deal. If the margin is wide, then a massive breakout of LDP reformists becomes more likely. That will be the end of the LDP as we know it, as any remaining reformists become an uncomfortably dwindling minority. Note also that in the DPJ, old-school sympathizers of recent DPJ defectors Hideo Watanabe et al will become more expendable as a result.
Paradoxically, if my analysis is correct, the LDP is likelier to collapse the smaller the margin of defeat. But this is all highly speculative. Without parallel universes in which the Lower House election is played out in infinite numbers, there is no way of knowing for sure.
That’s it for now.