Media surveys have shown the Democratic Party of Japan is on track for a huge victory over Prime Minister Taro Aso's Liberal Democratic Party (LDP), which has ruled the country for all but 10 months since its founding in 1955.
A clear Democratic Party win in the lower house election would break a deadlock in parliament, where the party and its allies have controlled the less powerful upper chamber since 2007, allowing them to delay legislation.
At last, it is the election tomorrow, one that we will be able to tell the next generation changed Japanese history, Democratic Party leader Yukio Hatoyama told a crowd in the city of Sakai in western Japan.
Aso sought to rally voters in Tokyo, where the Democratic Party trounced the LDP in a metropolitan election in July.
He accused the decade-old Democrats of being weak on security and said the ruling party deserved credit for steering the economy back to growth in the second quarter after Japan's longest recession since World War Two.
I beg you to give power to the LDP so we can complete the recovery, Aso told 500 mainly LDP supporters at a train station.
The Democrats have promised to focus spending on households with child allowances and aid for farmers while wresting control of policy from the hands of bureaucrats.
Figures released on Friday showed the jobless rate in the world's second-largest economy hit a record high of 5.7 percent in July. The statistics also showed deflation was taking root for the second time in less than five years.
A survey in the Asahi Shimbun newspaper said voter turnout could reach 70 percent, the highest in two decades, underscoring concern among Japanese about their country's future. Turnout was 67.5 percent in the last lower house poll in 2005.
Whoever wins the election on Sunday, we want to ask the next administration to swiftly deal with concerns about unemployment uncertainty and deflation, which are deepening simultaneously, the Nikkei business daily said in an editorial on Saturday.
RAPIDLY GREYING NATION
For many voters, the biggest issues are the struggling economy and the country's aging and shrinking population.
Japan is currently the world's 10th-largest country in terms of population, with more than 127 million people. By 2050 it is forecast to rank 18th with 93.7 million, according to the U.S. Census Bureau.
Japan is also graying more quickly than any other developed country, inflating social security costs. More than a quarter of Japanese will be 65 or over by 2015.
Analysts have cautioned that voter anger at the LDP is more due to scandals and a perceived inability to solve Japan's deep problems rather than enthusiasm for the Democrats.The government now is just not effective. I am not sure if the Democratic Party is good or bad, for now I just want change, said Kotaro Kobayashi, a 75-year-old retiree in Tokyo.
Financial markets would welcome an end to the deadlock in parliament but the Democrats' spending plans and vow to keep the sales tax at 5 percent for the next four years have raised concerns that Japan's already huge public debt will grow further.
Some Japanese newspapers have said the Democrats are likely to win a two-thirds majority in the 480-member lower house.
(Additional reporting by Colin Parrott, Writing by Dean Yates, Editing by Nick Macfie)