Voters gave a cold shoulder to the governing Liberal Democratic Party and a big boost to the opposition Democratic Party of Japan in Sunday's triennial Upper House election, which was contested mainly over pension reform and Self-Defense Forces participation in the multinational force in Iraq. With the LDP-New Komeito coalition maintaining a solid majority, however, it is certain that Prime Minister Junichiro Koizumi will remain at the helm.

Of the 121 seats at stake, the LDP won 49, two seats short of the targeted number it held before the election, while the DPJ increased the number of its re-elected seats to 50 from 38. The DPJ now holds 82 seats in the 242-seat Upper House, compared with the LDP's 115. The coalition parties combined have 139 seats, including Komeito's 24. They also enjoy a majority in the more influential Lower House. The LDP setback is a wake-up call to Mr. Koizumi and his administration. It is a reminder that a majority of people are unhappy with his job performance, particularly his handling of the pension and Iraq issues. With his approval ratings falling sharply, it is likely that Mr. Koizumi will have a more difficult time holding his grip on power.

The dramatic gain for the DPJ -- which also won big in last November's general election -- is a fresh sign that Japan's fragmented political world is headed for a two-party system. The party's new president, Mr. Katsuya Okada, who took the post in May, is believed certain to win re-election in September's party leadership contest. The DPJ now appears to be in a better position to challenge the LDP in the next general election.