Prime Minister Shinzo Abe’s ruling coalition has secured a majority in Japan’s upper house of parliament, according to vote counts by public television and other media.
Exit polls indicated Mr Abe could even close in on the super-majority needed to propose constitutional revisions.
NHK public television said Mr Abe’s Liberal Democratic Party and its junior partner Komeito had won 64 seats in the upper house after two hours of vote counting.
The two-thirds majority needed for constitutional revision could be within reach if the ruling bloc can gain support from members of another conservative party and independents.
Up for grabs were 124 seats in the less powerful of Japan’s two parliamentary chambers. There are 245 seats in the upper house – which does not choose the prime minister – about half of which are elected every three years.
Mr Abe welcomed the result, saying it reflects a public mandate for his policies.
He said “I believe the people chose political stability, urging us to pursue our policies and carry out diplomacy to protect Japan’s national interests.”
Opposition parties have focused on concerns over household finances, such as the impact from an upcoming 10% sales tax increase and strains on the public pension system amid Japan’s ageing population.
Mr Abe has led his Liberal Democratic Party to five consecutive parliamentary election victories since 2012.
Mr Abe was hoping to gain enough upper house seats to boost his chances for constitutional revision, his long-cherished goal before his term ends in 2021. Mr Abe needs approval by a two-thirds majority in both houses to propose a revision and seek a national referendum. His ruling bloc already has a two-thirds majority in the more powerful lower house.
But Mr Abe and his conservative backers face challenges because voters seem more concerned about their jobs, the economy and social security.
At a polling station in Tokyo’s Chuo district on Sunday, voters were divided over Mr Abe’s six-and-a-half-year rule.
A voter who identified himself only as a company worker in his 40s said he chose a candidate and a party that have demonstrated an ability to get things done, suggesting he voted for Mr Abe’s ruling party and its candidate, as “there is no point in casting my vote for a party or a politician who has no such abilities”.
Another voter, Katsunori Takeuchi, a 57-year-old fish market worker, said it was time to change the dominance of Mr Abe and his ultra-conservative policies.
“I think the ruling party has been dominating politics for far too long and it is causing damage,” he said.