The ruling Liberal Democratic Party is set to become the largest party in the House of Councillors for the first time in six years, sharply increasing its seats from the 84 it held before Sunday's election for the 242-seat upper chamber, Kyodo News exit polls and early returns showed.
In addition to the 50 seats held by the party that were not contested in Sunday's election, the LDP is projected to secure over 60 seats, backed by strong support for Prime Minister Abe's economic policies. Before the contest, the main opposition Democratic Party of Japan had been the leading group in the upper house.
As the LDP and its coalition partner, the New Komeito party, control the House of Representatives, the ruling camp is expected to put an end to the divided Diet that has allowed the opposition to block legislation.
LDP Vice President Masahiko Komura said on an NHK program Sunday, "The general public gave us seats, hoping that we can manage the government in a stable manner. They're calling for a government that can make decisions."
LDP Secretary General Shigeru Ishiba welcomed the election results, saying the party will "brace itself for achieving its goals."
Seiko Noda, head of the LDP's decision-making General Council, warned of complacency following the party's landslide victory in the upper house election.
New Komeito is projected to maintain the 10 seats it held in the upper house before the election.
New Komeito leader Natsuo Yamaguchi, who won a seat in the Tokyo constituency, said the election outcome "clearly showed the intention of voters who seek a stable government."
As a coalition partner, New Komeito will "make the most of what it has," Yamaguchi said. "We will humbly accept (the election results) and will try to meet people's expectations."
New Komeito Secretary General Yoshihisa Inoue said the party will "say what it has to say" to the LDP.
The New Komeito party remains wary of amending Japan's Constitution.
Abe, who is eager to revise the post-World War II pacifist Constitution, has called for the amendment of Article 96 so that revisions can be put to a referendum following majority votes in both houses of parliament, rather than two-thirds at present.
But the LDP and two opposition parties that support amending the Constitution are unlikely to secure the two-thirds majority in the upper house required to ease the rules for changing the supreme law.
Ishiba said on a radio program that the issue of constitutional amendments is yet to gain understanding from other parties and the Japanese people in general.