TOKYO — As the polls opened Sunday for Japan's most important election in decades, the question seemed to be not whether the opposition would defeat the long-governing Liberal Democratic Party, but by how big a margin.
Recent surveys show that the main opposition Democratic Party is likely to win well over 300 of the 480 seats being contested, giving it the majority needed to choose the next prime minister. Such a victory, which would be driven by voter discontent with Japan's long economic and political stagnation, would unseat the incumbent Liberal Democrats for only the second time since 1955.
There has even been concern here that the margin of victory could be too big. Some in the media have said a landslide could let the Democrats simply replace the Liberal Democrats as a dominant party, instead of creating the competitive two-party democracy that many had hoped would emerge from this election.
With even Liberal Democrats warning of a new "one-party dictatorship," the Democratic leader, Yukio Hatoyama, has repeatedly promised that his party would avoid the heavy-handed tactics abhorred in Japan's consensus-driven political culture.
"We will not force through anything and everything by sheer force of numbers," Hatoyama said in a speech on Wednesday.
Still, the tone of conversations on Japan's talk shows and on the streets is a mixture of thrill and anxiety about the imminent end of more than a half-century of Liberal Democratic rule. It remains unclear if a switch would bring a big change in Japan's direction, as the two centrist parties are close on most policies.
Rather, the nation has been transfixed by the saga of the governing party's kingpins fighting for their political lives amid the anti-incumbent sentiment. Tabloids have reveled in reporting on former prime ministers and party power brokers in losing battles against largely unknown opposition candidates, many of them charming younger women widely referred to as "assassins" because of their devastating political effect on their opponents.
One former prime minister, the gaffe-prone Yoshiro Mori, 72, drew the ire of many when he told voters not to be fooled by the "sexiness" of his opponent, a 33-year-old former temporary worker named Mieko Tanaka.
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The Liberal Democrats are fighting back by mobilizing their own younger lawmakers, many of them also women, to campaign for older male colleagues.
One is Yuko Obuchi, 35, the daughter of a former prime minister, who is the special minister in charge of improving Japan's low birthrate and is herself more than eight months pregnant.
On Friday, she campaigned in a working-class Tokyo neighborhood on behalf of Akihiro Ota, the leader of the New Komei Party, a Buddhist party that backs the Liberal Democrats. Ota, 63, is in a tight race with a woman representing the Democratic Party, Ai Aoki, a cheerful 44-year-old former kindergarten teacher.
Obuchi stood in front of a crowd of Liberal Democratic supporters and, rubbing her extended belly, began by saying she could give birth at any moment. "I tell my baby not to come out until after Aug. 30, because Mom's busy till then," she joked.
She then criticized the Democrats' promise to raise the birthrate by paying families stipends of $270 per month per child.
"They tell you sweet nothings," Obuchi warned, without offering an alternative plan.
Listeners seemed resigned that the party would lose. But they said wanted to see Obuchi instead of the unpopular Liberal Democratic leader, Prime Minister Taro Aso, because she gave the party a fresh face.
"The party needs to get rid of its old image," said Hideo Shiba, 68, who owns a small construction company. "She symbolizes the future of the Liberal Democratic Party."