Experts say the results of Sunday's election illustrated continuing anger over government scandals and missteps by Prime Minister Shinzo Abe's government, and the government's loss of 50 million pension records.
Analysts said the bruising defeat also indicated that ordinary voters are far more concerned with the economy, which affects their daily lives, than with Mr. Abe's emphasis on revising the country's pacifist constitution and introducing a more patriotic educational system.
The Mainichi newspaper said in a post-election editorial that the people had said noEto Mr. Abe's agenda, which, the paper said, is focused on ideology, and not on their everyday lives."
The election left Mr. Abe's Liberal Democratic Party with less than half the seats in the 242-seat upper house of parliament - the first time in post-war history that the LDP has not held majorities in both houses. The opposition Democratic Party of Japan will now dominate the upper house.
Media outlets, commentators, and politicians are calling on Mr. Abe to step down, but he is insisting he will stay in office. Looking sullen and downcast at a news conference Monday, he said he could not contemplate resignation.
"It is my duty to stay on as prime minister, and push my policies. However, the severe election result is my responsibility," Mr. Abe said.
LDP officials say Abe does not think his defeat was a rejection of his agenda. However, Hidenao Nakagawa, secretary-general of the LDP, did resign Monday morning to take responsibly for the historic defeat.
Mr. Abe noted Monday that his party still has a majority in the more powerful lower house, which confirms the majority party's selection of prime minister.
Ichiro Ozawa is leader of Democratic Party of Japan, which was the big winner in Sunday's election. He promised to fight for elections in the lower house.
But Mr. Abe indicated that he would resist calls for early elections there.
"We are still the majority in the lower house and we have two more years until there is another election. We will prove to the people that our party is competent and we will perform well," Mr. Abe said.
On Sunday, the LDP won only 37 of the 121 seats up for re-election, while the Democratic Party won 60. Half the seats in the upper house were being contested.
The losers Sunday included Toranosuke Katayama, a leader of the LDP's delegation in the upper house. He lost to Yumiko Himei, a 48-year-old women who formerly held a seat in a prefectural assembly. Another loser was Yuko Tojo, the granddaughter of Hideki Tojo, Japan's World War Two leader, who was hanged as a war criminal.