(Reuters) - Japan holds an election for parliament's lower house on December 16, with opinion polls suggesting that the long-dominant Liberal Democratic Party (LDP) will return to power after three years in opposition.
Below are some key facts about Japan's political parties.
(For a graphic charting voter preferences among major parties, click on: link.reuters.com/xyc34t)
2009 lower house election result: 308 out of 480 seats
Formed in a merger of several opposition parties, the DPJ swept to power in 2009 to end more than half a century of almost unbroken Liberal Democratic Party rule. It campaigned on a promise to break up the "iron triangle" between the powerful bureaucracy, business and LDP lawmakers, pay heed to consumers' interests and put elected officials in charge of policy.
Leader Yoshihiko Noda, 55, is already Japan's sixth prime minister since 2006 and the third from the DPJ. Noda, a former finance minister, made raising the sales tax his top goal even though it was not part of the DPJ's 2009 campaign platform.
The Democrats' support slumped over what voters saw as broken promises, a confused response to last year's tsunami and nuclear crisis and Noda's embrace of unpopular causes such as the tax hike and the restart of nuclear reactors.
2009 election result: 119 seats
Until the 2009 election, the party, which has nurtured close ties with business and the bureaucracy, has been in power alone or in coalitions almost non-stop since its founding in 1955.
Its leader, Shinzo Abe, 58, prime minister in 2006-2007, has said he would not yield in a territorial row with China but would try to mend economic ties with Japan's giant neighbor. Abe has also said he would increase defense spending if needed.
Abe has piled pressure on the central bank to ease monetary policy further and adopt a 2 percent inflation target and might delay the sales tax rise if deflation persists. The party favors a key role for nuclear power in Japan's energy mix despite a dramatic shift in public opinion in favor of phasing out atomic energy after the Fukushima crisis.
Website: j-ishin.jp/(Japanese only)
Popular Osaka Mayor Toru Hashimoto, 43, formally launched the right-leaning party in September to woo voters fed up with the two main parties.
His core policies include shrinking the role of the central government, more market competition and cuts in corporate and income taxes.
Last month, the party merged with a few conservative lawmakers led by former nationalist Tokyo Governor Shintaro Ishihara, 80, in a bid to build an influential "third force".
The party wants to boost defense spending and maritime surveillance in response to a territorial row with China.
It has flip-flopped on nuclear power after merging with Ishihara's pro-atomic group, and confusion persists.
2009 result: 21 seats
The party founded by members of a Buddhist sect, the Soka Gakkai, is a former LDP ally and expected to be in any coalition led by the larger conservative party.
It tends to focus on economic policies for the less well off and is more moderate on security issues than the LDP.
Website: www.nippon-mirai.jp/ (Japanese only)
Yukiko Kada, governor of the western Japanese prefecture of Shiga and former environmental sociology professor, launched the party just days before the official campaign kicked off to bring together anti-nuclear forces.
Most candidates hail from a short-lived party founded by former DPJ leader Ichiro Ozawa, 70, which opposes tax increases, nuclear power and participation in a U.S.-led trade pact, the Trans-Pacific Partnership (TPP). Ozawa has been nicknamed the "Destroyer" for his role in creating and then breaking up parties he has formed since he left the LDP in 1993.
Ozawa's group had 48 seats in the lower house before its dissolution, making it the third-largest in the chamber.
Kada aims to shut down all nuclear reactors within 10 years, much sooner than the DPJ's goal to phase out nuclear power by the 2030s, and wants to improve conditions for working women to boost the birth rate and stimulate economic growth.
Website: www.your-party.jp/ (Japanese only)
2009 election result: five seats
Formed by former LDP lawmaker Yoshimi Watanabe shortly before the 2009 polls, the party calls for Japan's participation in the TPP, advocates an early exit from nuclear power and would suspend the planned rise in the sales tax. It also favors aggressive monetary stimulus.
The spiky-haired Watanabe has cultivated ties with Hashimoto and lost some members to his group.
Compiled by Kaori Kaneko, Tetsushi Kajimoto, Kiyoshi Takenaka and Antoni Slodkowski; Editing by Ken Wills