A historic opposition election victory has raised chances of a new era in Japanese politics, with the conservative ruling party finally seeing a real challenge after half a century in power, analysts said on Monday.
Prime Minister Shinzo Abe's Liberal Democratic Party (LDP) lost nearly half of the seats it was defending in Sunday's upper house polls, tumbling from the largest party in a chamber for the first time since it was founded in 1955.
The main opposition Democratic Party of Japan (DPJ) is set to control a chamber of parliament for the first time -- although some cautioned that the election was more a ruling-party defeat than an opposition victory.
"Japanese politics are now facing a crucial turning point," said Hidekazu Kawai, honorary professor of politics at Gakushuin University in Tokyo.
"It's not the first time to see a sign of a change in Japanese politics, but this appears to be the beginning of the end to the 1955 regime," Kawai said.
If the DPJ proves it can govern, "Japan will take a step closer to being a country with a sound political system, like other developed countries."
The LDP has been in power in the world's second largest economy for all but 10 months since it was formed, thriving on support from businesses, rural voters and the bureaucracy.
It can remain in power even now, as it still enjoys a wide majority in the more powerful lower house won under Abe's popular predecessor Junichiro Koizumi -- who styled himself as a reformist out against the LDP's vested interests.
The DPJ, led by the famously shrewd former LDP strongman Ichiro Ozawa, won over voters in traditional LDP strongholds by tapping into anger against Koizumi's free-market reforms, including the scaling back of public services.
But analysts warned that the DPJ, formed in 1998 between LDP dissidents and former socialists, risked unravelling under the weight of its contradictions.
"This was not an election in which people voted to have the DPJ take over the government. They voted against Prime Minister Abe," said Gerald Curtis, a Japan expert at New York's Columbia University.
"The DPJ is not ready to take over power. They should hope that Abe holds on for as long as possible while they try to get their act together."
Abe refused to step down, saying the election mauling was due to scandals such as mismanagement of the pension system and not a rejection of his conservative ideas.
The DPJ itself is divided on Abe's agenda. Ozawa is a longtime advocate of Abe's signature issue -- rewriting the US-imposed post-World War II pacifist Constitution.
"It is too early to say if a two-party system can become rooted in Japan," said Tetsuro Kato, professor of politics at Hitotsubashi University in Tokyo. "The next stage is general elections, and the question is if the DPJ can maintain this momentum until then."
The LDP-led coalition can use its sweeping majority in the lower house to override votes in the upper house, setting the stage for policy deadlock.
Fresh from victory, the upbeat opposition camp urged Abe to dissolve the lower house -- which could bring a change in power.
But analysts warned the DPJ should be careful what it wished for.
"To take power, the DPJ needs to coordinate its basic policy principles," said Shujiro Kato, professor of politics in Toyo University.