Yukio Hatoyama is Japan's fourth prime minister in a row to last for less than a year, and the 14th to hold the post in 21 years. Many PMs have risen as part of a political dynasty without having to hone leadership skills.
Yukio Hatoyama comes from four generations of politicians from the ruling LDP, which his DPJ party just ousted from power.
The Democratic Party of Japan has promoted women and younger candidates who have not risen through traditional routes to power.
Prime Minister Aso's long-ruling party is under fire as polls indicate strong support for the opposition Democratic Party of Japan. The vote is Aug. 30.
The Aug. 30 vote could end its nearly uninterrupted half century in power.
Japanese Prime Minister Taro Aso ended a two-day trip to Beijing Thursday. Both countries affirmed their desire to cooperate but avoided troublesome topics.