The fate of the nation's nuclear power program, its long-struggling economy, the sales tax hike, and recent strained ties with China and South Korea will be key points for voters to consider in the Dec. 16 Lower House election, for which official campaigning started Tuesday.

Opinion polls suggest the election will bring an end to the Democratic Party of Japan's three-year rule and see the Liberal Democratic Party, which the DPJ ousted in the 2009 election, re-emerge as the strongest force, albeit without a majority.

With 12 parties vying for the 480 Lower House seats, the focus has turned to the role unaffiliated voters will play in determining the outcome of the poll and what kind of ruling coalition will be subsequently formed.