Japan goes to the polls on 14 December on a very odd pretext. Prime Minister Abe, in calling an election yesterday, justified dissolving the lower house only half way into his four-year term on the grounds that he needed a mandate to defer raising the consumption tax from 8% to 10% in October 2015. The scheduled tax rise was legislated by the former DPJ-led government of Yoshihiko Noda. Abe again stated last night on NHK's much watched 9pm news service that the DPJ Government had failed badly because it had not included the consumption tax plan in the manifesto it was elected on.

In essence, Abe is arguing that he needs an election mandate to defer a tax rise that did not have a public mandate in the first place.

Even more strangely, all the main political actors, including the DPJ, agree with deferring the consumption tax rise. Opposition to deferral emanated primarily from fiscal conservatives within the LDP itself, such as party secretary-general Sadakazu Tanigaki, and from some academic advisers. The LDP holds a majority in both houses of the Diet and can enact legislative change without taking the issue issue to an election. Moreover, when the DPJ legislated for a timetable of consumption tax rises, it incorporated provisions in an annex to the bill that foreshadowed deferral of the rise if economic circumstances were unfavourable.

As indeed they are now. The LDP's snap election strategy, much leaked and publicly discussed over the last week, has been sideswiped by unexpectedly bad economic data. Abe found himself on Tuesday night calling an election just a day after new statistics had Japan officially in recession. The July-September quarterly data, contrary to market expectations of around a 2% rise, came in at a dismal annualised minus 1.6%.

So why an election now?

Two ministerial resignations soon after Abe's August ministerial reshuffle, which was supposed to offer a fresh line up to carry his government for at least another year, is apparently a factor. The LDP also has precedents for successful early elections, including Yasuhiro Nakasone's strong victory in June 1986 and Junichiro Koizumi in August 2005. Moreover, former PM Taro Aso, now deputy leader and finance minister, is widely thought to have waited too long in going to the polls in 2009, compounding the scale of the LDP's defeat. In short, things can only get worse. According to one well-placed insider, LDP leaders expect to lose about 20 seats on 14 December.

Oppositional politics is fragmented. The DPJ has reasonable leadership under Banri Kaeda but remains severely weakened by the scale of its November 2012 defeat and the earlier divisions that saw the departure of Ichiro Ozawa and his 50-odd supporters. The main threat to Abe's LDP would come from effective coordination on electoral strategy between the DPJ and Your Party (Minna no Tou). Yet the latter is hampered by leadership divisions, as the popular Yoshimi Watanabe stepped down from the leadership in April during an investigation of a personal loan received from the chairman of a cosmetics company to cover personal debts.

The various opposition parties offer numerous but divided voices critical of the Government. Each will struggle for attention as the campaign develops. The LDP meanwhile benefits from support from Keidanren, a peak business organisation which has renewed political donations to the party and is supportive of Abenomics, and from effective media management and grassroots organisation.

Yet Abe might find he is fighting the election on rather more issues than he hopes.

Many Japanese have not forgotten the policy decisions he pushed through, such as constitutional reinterpretation of Article 9 to allow collective security, and a new national secrecy law. These were major policy developments that ran against the grain of postwar political culture and which he did not articulate clearly to the electorate in the November 2012 campaign, nor in the upper house election in July 2013.

It is no surprise then that opposition politicians and critics are declaring this to be a diet dissolution without a pretext, and mocking Abe's tangled logic on needing a mandate to reschedule a consumption tax rise, a policy move that has broad political support anyway.

The most optimistic explanation for Abe's snap election move is that he wants a full four-year term to pursue seriously the so-called 'third arrow' of Abenomics: radical economic reform. There are tentative signs that he is prepared to push major changes upon traditional LDP-supporting sectors such as agriculture (the powerful agricultural cooperatives will lose their exemption from anti-monopolies law, although Abe has retreated from a more radical plan to break them up). With President Obama facing a Republican-controlled Congress, he and a re-elected Abe might be able to lead TPP negotiations to a clean agreement.

These are some of the hopes and fears that will animate electoral politics in Japan between now and 14 December. The money is obviously on the LDP, due to its fund-raising ability and capacity to get out the vote in a country when many are too alienated from politics to bother to vote. Yet Abe may yet find his margin of dominance shaved closer than LDP strategists imagined when they decided to dash to an early election.

Photo by Flickr user James Hadfield.