|Hatoyama's victory would mark a seismic shift in Japanese politics [Reuters]
If opinion polls prove correct, Yukio Hatoyama stands within reach of becoming Japan's next prime minister.
His appointment would mark a dramatic shift in Japanese politics, ending five decades of almost unbroken rule by the Liberal Democratic party (LDP).
Appointed to lead the opposition centrist Democratic Party of Japan (DPJ) three months ago, Hatoyama has a strong political pedigree.
He is the grandson of a former prime minister, the son of a one-time foreign minister and the brother of a recently resigned cabinet minister.
He also has close ties to Japan's business elite – his grandfather founded the Japanese tyre giant Bridgestone – and is Japan's wealthiest parliamentarian.
Originally trained as an engineer at California's Stanford University, Hatoyama won a lower house seat in Hokkaido as a candidate for the governing LDP.
In 1993, however, he quit the party along with several other defectors from the LDP, in a move that temporarily ousted it from power.
Three years later he co-founded the DPJ, going on to lead the party for the first time from 1999 to 2002.
More recently he served as the DPJ's secretary-general, before being returned to the party's presidency in May this year after a political donations scandal forced the resignation of Ichiro Ozawa.
Heading into one of Japan's most hotly-contested elections in decades, Hatoyama has sought to play down his wealthy roots, pledging to fight for the common man and promising an Obama-style message of change after decades of LDP rule.
Promoting his vision of what he calls a "fraternal society" and a "new Japan", he has promised a radical shake-up of the way the world's number two economy is governed.
Among the measures he has said a DPJ government would take are strengthening Japan's social welfare safety net, cutting government waste, cleaning up campaign financing and ending the strong influence of state bureaucrats.