TOKYO — Two days after Japan’s former prime minister Shinzo Abe was gunned down at a campaign stop on Friday, his Liberal Democratic Party and its allies swept to victory in a parliamentary election that gave them a chance to pursue Mr. Abe’s long-held ambition of revising Japan’s pacifist Constitution.
It was the clearest sign that Mr. Abe, Japan’s longest-serving prime minister, remained a guiding political force. Even before his death, he was no longer leader of the country or its governing party, but his legacy shaped voters’ choices at the ballot box and his party’s vision for the future.
“I have the responsibility to take over the ideas of former Prime Minister Abe,” the current prime minister, Fumio Kishida, told a crowd west of Tokyo on Saturday, the day after Mr. Abe’s killing, as he campaigned for their party’s candidates for the Upper House of Parliament.
The Liberal Democrats and their coalition partners gained enough seats in Sunday’s election to form a crucial two-thirds supermajority. They can now amend a clause in the Constitution, imposed by postwar American occupiers, that renounces war. That long-held goal would open the door for Japan to become a military power, capable of global leadership.
By the early hours of Monday morning, the Liberal Democrats, together with Komeito, their longtime partner, and other allied parties, had won 87 seats, giving them more than 70 percent of the Upper House, besting their last supermajority in 2016. (A similar coalition commands more than two-thirds of the Lower House.)
Mr. Abe’s death appeared to have helped increase voter turnout slightly, to over 52 percent, up from about 49 percent in the last Upper House election in 2019.
As returns rolled in, Mr. Kishida said he hoped to “gain people’s understanding” and “deepen the discussion” about the party’s proposal for revising the Constitution.
Even with the supermajority, much stands in the way of the plan — not least that it has long been unpopular with the Japanese public. And with inflation pressures mounting, the yen weakening and coronavirus infections again on the rise, changing the Constitution could be a harder sell than ever.
“I’m interested in prices, wages, daily life, medical services and child care,” said Risako Sakaguchi, 29, who cast her votes for Liberal Democratic candidates at a polling station in Saitama, a suburb of Tokyo.
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With such fundamental concerns, “constitutional revision is a kind of luxury good,” said Tobias Harris, a senior fellow at the Center for American Progress who oversees work on Asia.
“Given that attention being spent on constitutional revision is attention not being paid to other stuff, there is going to be a penalty for it,” Mr. Harris said, “especially when people are so concerned about household issues.”
Unshackling Japan’s military was a cherished goal of Mr. Abe, but without him, the will to push through a difficult parliamentary process could wane.
“Now that he is gone, there is no clear leader among the L.D.P. senior members who will push through the constitutional revision,” said Hiroshi Nakanishi, professor of politics at Kyoto University.
Mr. Abe, who was in office for nearly eight years (in addition to a brief, earlier stint as prime minister), left a legacy that went well beyond his hopes of revising the Constitution.
Even after Japan fell behind China in world economic rankings, he helped extend its influence by holding a multinational trade agreement together after President Donald J. Trump pulled the United States out of it. At home, he helped bring the economy back from years of being in the doldrums. Even if his economic policies never delivered as much as he promised, he gained international recognition for the program he called “Abenomics.”
After he left office, Mr. Abe’s public statements resonated well beyond those of most former prime ministers. He suggested that it was time for Japan to establish a nuclear sharing agreement with the United States. Media outlets then assumed the Liberal Democrats were considering a break with the longtime taboo against even discussing the possibility of a Japanese nuclear arsenal.
Within the party, he was a kingmaker, often referred to as a “shadow shogun.” Mr. Kishida owes his position to Mr. Abe, who directed his supporters to throw their weight behind him after Mr. Abe’s first choice, Sanae Takaichi, lost a first-round ballot in the party leadership contest.
Campaigning for Liberal Democrats over the last two weeks, Mr. Abe’s enduring influence was on display, drawing crowds as far north as Hokkaido and as far south as Fukuoka. His fatal visit to Nara, Japan’s old capital, was his second in support of Kei Sato, 43, a junior member of the party.
For Mr. Kishida, the sudden loss of Mr. Abe may present opportunities as well as perils. He could consolidate power after the election, as he is not legally required to call another one for three years. Politicians in Japan often refer to this interval as the “golden period.”
But history suggests the odds may be against him. Since the end of World War II, powerful prime ministers have typically been followed by a revolving door of forgettable faces, said Carol Gluck, a professor of history and specialist in modern Japan at Columbia University. Mr. Kishida is the second person to hold the job since Mr. Abe resigned in 2020; his predecessor, Yoshihide Suga, lasted just a year.
“There’s a whole lot of prime ministers, if you add them up between 1945 and now, who did not make a mark,” Professor Gluck said.
Privately, Mr. Kishida may feel some relief that he will no longer have to answer to Mr. Abe. But others in the party are sure to maneuver to fill the power vacuum.
Mr. Abe led the largest, and most right-leaning, party faction, and he had not anointed a successor. Infighting could unsettle the party and make it more difficult for Mr. Kishida to get policies enacted.
“It would have been much more predictable if Abe was still a big influence,” said Koichi Nakano, a professor of politics at Sophia University.
Party power squabbles aside, the bigger question may be whether Mr. Kishida ultimately has his own vision.
He once cast himself as a liberal-leaning, dovish member of the party. But driven by the war in Ukraine and increasing threats from North Korea and China, Mr. Kishida has followed Mr. Abe in calling for increased military spending and weapons that can strike missile launch sites in enemy territory.
Without Mr. Abe as a driving force, though, some analysts wonder if Mr. Kishida will be able to deliver on that national security agenda.
“I think Japan will lose our momentum to strengthen our defense,” said Lully Miura, a political scientist and head of the Yamaneko Research Institute in Tokyo. “We need a visible figure who can support the strong security and appeal to the public.”
At the peak of his power, Mr. Abe himself was unable to push through the constitutional revisions he so badly wanted. In 2016, he presided over a Parliament in which his governing coalition had the required two-thirds supermajority. But tensions within the coalition, along with concern that the public — which must ultimately ratify any constitutional amendment — would not go along, thwarted his hopes.
Changing the Constitution could be even further out of reach now, given multiple crises around the world and at home.
The war in Ukraine has worsened supply chain problems and driven up the prices of oil and other commodities, raising fears of energy shortages in Japan. Coronavirus infections, until recently under control, have started rising again. And in the longer term, an aging population and falling birthrate raise the prospect of labor shortages and problems with caregiving.
Mr. Kishida has offered no all-encompassing program to address such challenges. When running for the party leadership, he spoke of a “new capitalism,” but never spelt out what that meant, other than vague rhetoric about reducing inequality.
“Kishida could get things done if there are things that he wants to get done,” said Nick Kapur, a historian of modern Japan at Rutgers University. “He has some popularity and he’s going to have a majority, but as we know, there are so many economic headwinds for everyone in the world — dealing with inflation and an emerging markets debt crisis and the war in Ukraine — and maybe that would damage any leader at some point.”
Ayumi Sekizawa, 31, who works for a real estate company in Tokyo, said he had voted for the Liberal Democrats in part to show his support after Mr. Abe’s death. But he said he usually voted for them because there were “no other good parties.”
He said that given the aggressive behavior of Russia, China and North Korea, he agreed that Japan needed to improve its defense capabilities.
But his main concerns were closer to home. “I’m interested in the economy,” he said. “Wages should be raised, otherwise, virtually, our living standard is declining.”
Makiko Inoue, Hikari Hida and Ben Dooley contributed reporting.