Prime Minister Shinzo Abe's ruling coalition won a landslide victory on Sunday in an election for parliament's upper house, media exit polls showed, despite concerns about his economic policies and a goal to revise the pacifist constitution.
Some of the exit polls also showed Abe's coalition and like-minded parties had won the two-thirds "super majority" needed to try to revise the post-war constitution for the first time, though others only said the threshold was within reach.
Abe's Liberal Democratic Party (LDP) won a simple majority for the first time since 1989, according to the voter surveys, a victory that will bolster the premier's grip over the conservative party that he led back to power in 2012 after three years in opposition.
A push to ease the charter's constraints on the military operating overseas could lead to tension with China, where memories of Japan's past militarism still arouse anger.
Tomomi Inada, the LDP's policy chief, noted that the party had already crafted a draft revised constitution. "Our party is one that calls for reforming the constitution," she told local television shortly after the polls closed.
In Japan, financial market players fear amending the charter will divert Abe's energy away from reviving the stuttering economy.
Some voters who backed Abe's Liberal Democratic Party (LDP) said the economy's health was also their biggest concern.
"Especially since I see economic growth as the priority, I have little hope for the opposition parties," said Yoshihiko Takeda, a 36-year-old IT company employee.
Abe had cast the election as a referendum on his "Abenomics" recipe of hyper-easy monetary policy, spending and reform. With signs the strategy is failing, the government plans to compile a post-election stimulus package that could exceed 10 trillion yen ($99 billion).
But economists worry the government will choose big-ticket infrastructure projects rather than implement tough structural reforms.
Abe is expected to reshuffle his cabinet after the election.
His justice minister and the minister for Okinawa appear in danger of losing their seats, though neither is a heavyweight. Speculation has also emerged that Abe might replace Finance Minister Taro Aso, 75.
Media surveys have shown the ruling bloc is set to exceed Abe's target of 61 seats while his LDP could win a majority on its own for the first time since 1989.
A big win would allow Abe to assert he has a mandate for his economic and other policies, but any such claim would be undermined if turnout is low - a distinct possibility in a poll that has gained minimal media attention. The voting age has been lowered to 18 from 20 for the first time.
Abe's coalition won landslides in the last three general elections in terms of numbers of seats, but experts say rock-bottom turnout reflected voters' sense of a lack of viable alternatives.
The opposition Democratic Party has linked up with three smaller parties including the Japanese Communist Party to try to block the pro-constitutional revision camp from getting a super majority. But the Democrats suffer from an image as incompetent after their rocky 2009-2012 rule.
Conservatives see the constitution as a humiliating symbol of Japan's defeat in World War Two. Its admirers consider it the source of post-war peace and democracy. Revising the charter needs the approval of two-thirds in both houses of parliament and a majority in a referendum.
But a majority of voters see no need to revise the constitution and the LDP's dovish partner is reluctant to change its pacifist Article 9.
Noriko Okada, a 66-year-old interior decorator, said she voted for a Japan Communist Party candidate to show her opposition to constitutional revision.
"I'm no party member or supporter of the Communist Party, but I thought they were the farthest away from the LDP," she said. "My ballot came from despair, rather than hope. I'm concerned about the Abe government."