Aso, 67, is widely considered the favorite. As LDP Secretary General, he is in the position closest to LDP president. He has an outstanding resume and incomparable political resources. In addition to his term as LDP Secretary General, he was Foreign Minister under Abe and Junichiro Koizumi and has served in the House of Representatives since 1979. He is the fourth generation of a political family that includes former Prime Ministers Yoshida Shigeru and Zenko Suzuki.

Meanwhile, the 56-year-old Koike faces an uphill battle in her campaign to become Japan's first female prime minister.

In candidate statements published in the Daily Yomiuri on September 8, Taro promised to reduce income tax and boost government spending to revive the economy, while other candidates called for higher tax rates and economic reform.

Whoever the new prime minister is, the winner is not playing a funny political game, said Liu from Tsinghua University. In the face of strong political opposition, the new prime minister must make enough economic headway to maintain public support.

Liu Junhong, a researcher at the Institute of Japanese Studies, China Institutes of Contemporary International Relations (CICIR), published an article in Outlook Weekly explaining the current political and economic situation in Japan.

In recent decades, Japanese politics has become unstable. The fight between the LDP and the DP, which was formed when several smaller parties merged in 1998, prevents the two-party system from properly maturing. It is no surprise that prime ministers tend to resign frequently and suddenly, as neither party is able to gain majorities in both houses and the opposition party in each house constantly seeks to undermine the ruling one. Meanwhile, the only way smaller parties can exert influence is to form ruling coalitions with the LDP and the DP. "These smaller parties now embrace utilitarianism rather than loyalty to a certain ally, which increases instability in ruling coalitions," Liu from the CICIR concluded.

Japan has all the problems of a developed economy, Liu said, including slower economic growth and a decreased ability to compete internationally. At the same time, a sliding birth rate, aging population and widening income gap have strained social programs. "To solve all these political and economic problems, the new prime minister needs to reform Japan's party system and economic structure," Liu said.