With a sweeping victory for the DPJ now a fact, party leader Yukio Hatoyama is certain to replace Taro Aso as Japan's leader. The scion of a conservative dynasty and the grandson of a former prime minister, the 62-year-old former academic has raised conservative hackles by promising what he calls a "new deal" in economic, environmental and defence policies, switching government emphasis from big business to consumers and ending Japan's traditional subservience to the US military.
"The Cold War has ended, along with the direct threat from Russia, but we're still in Cold War mode," he told The Independent. "In my home constituency of Hokkaido [in the north of Japan] there are still lots of tanks prepared to counter a Russian invasion. We're being told to show the flag in Afghanistan and put boots on the ground in Iraq, but are we really making a genuine contribution if we just go along with what America says?"
Mr Hatoyama also promises to, in his words, "go to war with" Japan's powerful bureaucracy, wrestling control over its budgets and freeing up billions of pounds in wasted taxes. He says he will switch resources from Japan's huge construction sector, traditionally dependent on LDP largesse, and put money into schools, hospitals and public buildings.
"And we would introduce an environmental new deal. We would aim to put solar panels in every home in Japan to reduce the cost of electricity, and provide government assistance for electric cars and so on."
Critics say those plans will cost much more than the Democrats claim, even if the party doesn't collapse under the weight of its ideological contradictions. Its origins 12 years ago were in a hybrid of political forces, including LDP refugees, hardline conservatives and socialists. Mr Hatoyama is a famous supporter of Japan's so-called pacifist constitution, which renounces war and is despised by conservatives, but many in his party want to revise it.
Despite talk of a radical break with the past, most analysts expect the DPJ to deliver more continuity than disruption to the world's second-largest economy.
"We don't have any intention of changing our position on the constitution," he insists. But Mr Hatoyama hints at closer co-operation with China. "We should consider some form of alliance in Asia and such an alliance might well be an option in the future."