TOKYO -- Japanese voters handed a landslide victory to the governing Liberal Democratic Party in parliamentary elections on Sunday, opening the possibility of dramatic changes in the long-paralyzed country, even as it returned Japan to effective one-party rule that seemed to thwart recent hopes for a more competitive democracy.
By securing control of both houses of Parliament for up to three years, the win offers Prime Minister Shinzo Abe, an outspoken nationalist who promises to revitalize Japan's stagnant economy and strengthen its military, the chance to be the most transformative leader in a decade. It also offered an opportunity to end the nation's series of short-lived and ineffective prime ministers.
The victory comes at a time when many Japanese seem more open than ever to change, after years of failed efforts to end the economic slump, and as an intensifying territorial challenge by China that has nudged this long-pacifist nation toward seeking a more robust military.
And unlike some of Japan's previous colorless leaders, Mr. Abe, 58, seems eager to become such an agent of change. He campaigned on promises to make fundamental, and possibly painful, changes in the economy. But his vows to stand up to China and rewrite Japan's antiwar Constitution to allow the legal right to maintain a full-fledged military, rather than self-defense forces, raising fears he will go too far and further isolate Japan in the region.
A week before the election, he became the first prime minister to visit a tropical island near the group of uninhabited islets at the heart of the dispute with China, and had earlier raised eyebrows by riding in a tank and climbing into a fighter jet in front of cameras.
"Abe has a pragmatic side and a strongly nationalistic side," said Hiroshi Shiratori, a professor of political science at Hosei University in Tokyo. "This election could free him up to do more of the latter, which is what he really wants."
At the same time, it remains unclear how far the Japanese people may be willing to let Mr. Abe go. The Associated Press, citing numbers from Kyodo News Agency, said 52 percent of voters went to the polls, one of the lowest turnouts since the end of World War II. While Sunday's results gave his ruling coalition a comfortable majority in the upper house, it fell short of the two-thirds that the Liberal Democrats and allies would need to revise the Constitution, something that has not happened since it was crafted by American occupiers after World War II.
As vote counting continued into the early hours of the morning, officials said the Liberal Democrats had won 65 of the 121 seats being contested. When combined with the 11 seats secured by its coalition partner, a small Buddhist party, the Liberal Democrats had taken enough seats to gain a majority in the 242-seat chamber.
The largest opposition group, the Democratic Party, suffered a humbling setback, securing 17 seats from voters who still blame it for failing to deliver on promises of overhaul after an election four years ago that ousted the Liberal Democrats in what had seemed to herald the advent of a vibrant two-party democracy. Before the vote on Sunday, one weekly tabloid criticized the impending return of the Liberal Democrats' effective monopoly as "a return to the ways of our ancestors."
Speaking to reporters after the victory, Mr. Abe thanked voters for ending the so-called twisted Parliament, in which opposing parties had split control of the two houses since 2007, adding to Japan's long political paralysis. But he admitted that he faced a challenge in convincing other lawmakers and also voters, who must approve any revision to the Constitution in a public referendum.
"There is still need to widen and deepen the debate on the Constitution," Mr. Abe said. "Voters have given us this new period of political stability, so we have time to deepen the debate."
He said he would also pursue an intermediate step of making the Constitution easier to revise by requiring a simple majority in Parliament instead of the current two-thirds. But making this change would require changing the Constitution, which means gathering enough votes.
Still, analysts said the win, coming seven months after Mr. Abe's party regained control of the lower house, had made overhaul of the Constitution feel like a real possibility for one of the first times since its adoption in 1947. In interviews outside polling stations, voters said that anxiety about China, and a hunger for leadership to restore Japan's international standing, made them willing to at least try some of Mr. Abe's ideas.
"I agree with Abe," said Noriaki Hibi, a 51-year-old telecommunications worker in the Tokyo suburb of Sayama. "Given the current situation with China, I think we need military preparedness."
But analysts said that support could fall once discussion turned to the specifics of constitutional change, with polls showing a majority of voters still opposing changes to the antiwar provisions. They also said much of the support for Mr. Abe rested on the popularity of his economic stimulus policies, known as Abenomics, which have already succeeded in starting Japan's $5 trillion economy on the road to a recovery.
"This is not unconditional support for Mr. Abe's whole agenda," said Jun Iio, a political scientist at the National Graduate Institute for Policy Studies in Tokyo. "Public support could evaporate if the economy starts to sour."
This article originally appeared in The New York Times.