The Democratic Party of Japan has swept the ruling party out of power in an historic election that could affect relations with the United States and the European Union.
The win brings an abrupt end to more than 50 years of nearly continuous rule by the Liberal Democratic Party led by Prime Minister Taro Aso.
"The results are very severe," Aso told reporters. "There has been a deep dissatisfaction with our party."
The DPJ is expected to win up to two-thirds of the seats in parliament, which would clear the way for the party to form a new government led by its leader, Yukio Hatoyama.
"This is a victory for the people," Hatoyama reportedly said Sunday. "We want to build a new government that hears the voices of the nation."
In Washington the White House released a statement Sunday that read in part: "As a close friend and ally, the United States awaits the formation of a new Japanese government. We are confident that the strong U.S.-Japan Alliance and the close partnership between our two countries will continue to flourish under the leadership of the next government in Tokyo."
Around 50,000 polling stations opened across Japan today for the crucial election.
"This election that's happening on Sunday in Japan is without exaggeration, the most important election in half a century," said Columbia University professor Gerald Curtis. "For half a century, there's basically been only one party in power -- and they are going to lose. They are going to lose very big."
Since World War II, with only a brief break in power, the Liberal Democratic Party (LDP) has ruled.
But early polls consistently showed the opposition party will win the majority of the 480 seats in the House of Representatives, which will then select the prime minister.
Hatoyama, the DPJ's leader, is a graduate of the University of Tokyo and holds a doctorate in engineering from Stanford University. He is also the grandson of former Prime Minister Ichiro Hatoyama.
"The public mood is this country is in decline," Curtis told ABC News. "The party that's been in power has not been able to do anything about it. The fact is, things have gotten worse."
Though Japan's economy has shown signs of coming out of its worst recession since World War II, the unemployment rate has hit a record high. Just two days before the election, the jobless rate was announced at 5.7 percent.
And in the world's second largest economy, for many people, it is all about business.
On the sidewalks of Tokyo, street vendors told ABC News that business has been "getting worse and worse." "People used to buy two items," the vendors said, "but now they only buy one."
Takao Masuda used to vote for the LDP, he said, from his pottery shop, but he doesn't anymore "because business has been down for the last 10 years."
When asked why their vote is for the opposition party, parents of two young children said simply, "For our kids' future."
"It's not that the DPJ is popular -- it's not particularly popular," said Curtis. "A kind of anti-LDP fever has spread like a contagious disease and everybody's catching it."
The question now is will a new ruling party be any better.
Hatoyama will be faced with the critical issues his campaign promised to change: the economy, low birth rates and an aging population.
Along with domestic concerns Japan's foreign policy and future relationship with the United States and China are at issue.