A staunch nationalist, Abe has railed 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.
Japan is going through a messy political transition, with a merry-go-round of prime ministers and the emergence of various parties to challenge the long-dominant LDP.
The DPJ ousted the LDP in a 2009 landslide, raising hopes for change. But the DPJ's failure to keep campaign promises and the government's handling of the nuclear crisis triggered by a March 11, 2011, earthquake and tsunami left many disillusioned. Noda's centerpiece achievement during nearly 15 months in office was a highly unpopular bill doubling the 5 percent national sales tax by 2015.
Polls show public support for the DPJ in the low teens, while 25 to 30 percent of voters back the LDP. Several other parties have lower levels of support, and nearly half the electorate is undecided.
"There are so many lying politicians," said Tokyo resident Michiyo Komaki. "I just wish for a leader who would do his job properly."
Ishihara recently resigned as Tokyo governor to create the Sunrise Party. As governor, he helped instigate the territorial crisis with China by declaring that Tokyo would buy and develop the disputed islands controlled by Japan but long claimed by Beijing. The central government bought the islands itself, intending to thwart Ishihara's more extreme plans, but China was still enraged.
Ishihara has been courting Toru Hashimoto, the young, outspoken mayor of Osaka, Japan's second-biggest city, in hopes of tapping voter dismay. Both have formed their own national political parties, but may not have enough time to get organized for the election.
The two men are reportedly in discussions to merge their parties and form a so-called "third force" to counter the LDP and DPJ, but apparently are struggling to reconcile conflicting policy views, including on nuclear power.
"The era of one-party dominance is clearly over and behind us," said Nakano, the professor. "We know what we are transiting from, but we don't know where we are going."
Associated Press writers Elaine Kurtenbach and Mari Yamaguchi contributed to this report.