Members of the ruling party have increasingly called for fresh leadership heading into elections. Others are already jumping ship — lawmaker Kotaro Nagasaki submitted his withdrawal from the party on Monday.

As prime minister, Aso can call for general parliamentary elections at any time, but they must take place by October. He had apparently been waiting, gambling that his political situation could improve, but the dire results of the Tokyo election seemed to have forced his hand.

On Monday, after the Tokyo results were released, Aso met with party leaders, who later said he would likely dissolve parliament next week after it passed legislation in the next few days, according to Osamu Sakashita, a spokesman for the prime minister's office.

Recent newspaper opinion polls have suggested the opposition party is well-placed to make major gains or even rise to power in the national election, with its leader Yukio Hatoyama likely to replace Aso.

That would mean the end of rule by the Liberal Democratic Party, which has governed Japan for all of the past 50 years, except a brief period in 1993.

However, that would still require a sea change in voter support. The Liberal Democrats currently have 303 seats in the 480-seat lower house, and its partner Komeito has 31. The Democratic Party has just 112.

Some Japanese voters said Monday that Aso should have waited before calling for general elections.

"I wish he had fought a bit longer," said Mineaki Kamada, 26, a worker in Tokyo.

Others, like Takuya Hayashida, 28, who also works in Tokyo, are ready for a change.

"I'd like to see a different Japan," he said.