Naoto Kan formally replaced Yukio Hatoyama as Japanese prime minister on Tuesday and said his administration would seek to rebuild the economy, state finances and social welfare systems. Both Kan and Hatoyama are leaders of the Democratic Party of Japan (DPJ) but that is perhaps where their similarities end.

Hatoyama is the scion of a political dynasty that is compared to the Kennedys of America. In contrast, Kan was born in 1946 into a salaried worker's family in Ube, Yamaguchi prefecture. Hatoyama was made for politics, winning his father's seat in Hokkaido to enter the House of Representatives as a Liberal Democratic Party member in 1986. In contrast, Kan started out at the grassroots level, working in citizens groups.

Though people view his success differently, Kan is generally known to live up to the public's expectation. And he not only has the experience, but also the political acumen to succeed in his endeavor.

Three factors work especially in favor of Kan. First, being one of the founders of the DPJ and having served as Japan's deputy prime minister makes him more suitable for the country's top job than any of his colleagues or competitors.

Second, during his stint as health and welfare minister, Kan won all-round praise for his role in uncovering a scandal in which more than 1,000 hemophiliacs contracted HIV because the blood they were administered was tainted. He exposed the medical racket by breaking bureaucratic resistance, something that was unheard of in Japan in 1996. He apologized to the victims too, something a Cabinet minister had not done before.

Last and the most important, Kan belongs to the neutral faction of the DPJ. He is the only figure who could win support from all the DPJ factions and avoid a power struggle. And perhaps that's why the party chose him as the country's leader.

The DPJ may get more support because of the change in leadership, but it will find it difficult to win a majority in the Senate election in July. It is likely to lose some seats in the Senate, but if the loss is restricted to less than 10 it could still retain majority by forming an alliance. And though it is not under threat of losing power even if it loses more than 10 seats, the new administration would face more difficulties in taking political decisions.

The Senate election may be very important for Kan to consolidate his power, but the more urgent task for him is to take measures to resolve thorny issues on the domestic political and diplomatic fronts.

Kan has four immediate missions to fulfil: reviving Japanese economy, easing the financial deficit, eliminating public discontent over a US military base on Okinawa island, and dealing with changes in East Asia's security.