Polls show that nearly half of the electorate is undecided on which party to support but it's clear that the ruling Democrats—in power for the last three years—are very likely to lose. That sets the stage for Japan to get its seventh prime minister in seven years.
Media reports say the elections will be held Dec. 16.
Although the opposition Liberal Democratic Party, which led Japan for most of the post-World War II era, would win the most seats in the 480-seat lower house, it would fall far short of a majority if elections were held now, according to the polls.
With no party a clear winner, Japan will end up with a coalition government made up of parties with differing policies and priorities. This could hinder decision-making as Japan wrestles with a two-decade economic slump, cleanup from last year's nuclear disaster, growing national debt and a rapidly aging population—not to mention a festering territorial dispute with China that is hurting business ties with its biggest trading partner.
"It's unlikely that the election will result in a clear mandate for anybody," said Koichi Nakano, a political science professor at Sophia University. "So in that sense, there's still going to be a lot of muddling through."
Japan must also decide whether it will follow through with plans to phase out nuclear power by 2040—a move many in the LDP oppose.
In a sudden turn of events, Noda abruptly said Wednesday in a one-on-one debate with LDP chief Shinzo Abe that he would dissolve parliament Friday if the opposition would agree to key reforms, including shrinking the size of parliament.
Abe, who said his party would go along with the measures, could get a second stab at being prime minister after his one-year stint in 2006-2007 if the LDP wins the most seats in the election.
A staunch nationalist, Abe has taken a strong stance against China in the dispute over a cluster of uninhabited islands in the East China Sea controlled by Japan but also claimed by China and Taiwan. Abe suddenly quit as prime minister in 2007, citing health problems that he says are no longer an issue.
"The day has finally come. Our battle starts today. Our mission to the people is to win this (election) battle," Abe told reporters earlier Friday.
Noda's Democratic Party of Japan won a landslide victory in 2009 elections amid high hopes for change, ousting the conservative, business-friendly LDP, which had ruled Japan nearly continuously since 1955.
But those hopes have been dashed amid widespread disgust with the DPJ's failure to keep campaign promises and the government's handling of the Fukushima nuclear crisis triggered by the March 11, 2011, earthquake and tsunami.
Voters are also unhappy with Noda's centerpiece achievement during his nearly 15 months in office: passing legislation to double the nation's 5 percent sales tax by 2015. He says the increase is necessary to meet growing social security costs as the country grays.
Recent polls show about 25-30 percent of voters back the LDP, while support for the DPJ is in the low teens. With scattered support for a few other parties, that leaves nearly half of the public undecided, meaning the outcome is still quite unclear.
"I really don't know who to vote for," said 62-year-old taxi driver Tetsuo Suzuki. "I voted for the DPJ in the last election, but they couldn't seem to get things done. I don't really want to go back to the LDP, either."
"Japan doesn't seem as perky as it used to be," he said, ticking off the economy and the territorial dispute with China as the two most pressing issues. "We want a strong leader who won't bend his principles."
Tapping into that voter dismay, outspoken leaders in the two biggest cities in Japan have decided to form their own national political parties, but they may not have enough time to get organized for the election.
The nationalistic governor of Tokyo, Shintaro Ishihara—who stirred up the flap with China by saying the Tokyo government would buy and develop the disputed islands called Senkaku by Japan and Diaoyu by China—resigned recently to create the Sunrise Party.
Toru Hashimoto, the brash, young mayor of Osaka, is working to draw up candidates for the newly formed Japan Restoration Party, although he said he himself will not run in the elections. Recent polls show his party has support in the 5 percent range.
The two men are in discussions, seeking a possibility to merge their parties and form a so-called "third force" to counter the LDP and DPJ, but it appears they are having difficulty reconciling some of their differing policy views, including on nuclear power.
Japan is going through a messy period of political transition with its merry-go-round of prime ministers and the emergence of various parties to challenge the long-dominant LDP, experts say.
"The era of one-party dominance is clearly over and behind us," said the professor, Nakano. "We know what we are transiting from, but we don't know where we are going."
AP writer Mari Yamaguchi in Tokyo contributed to this report.