TOKYO, NOV. 4 -- Japan's dominant Liberal Democratic Party won a special election today for an empty seat in the upper house of the Japanese Diet, or legislature, but the result seemed unlikely to help the LDP win passage of its controversial bill to authorize the dispatch of Japanese troops to help the multinational force in the Persian Gulf.

LDP candidate Yoshihisa Oshima won the upper house seat with a 45-percent plurality in a race against the candidates of the Japan Socialist Party and the Communist Party. Since both of the losing parties oppose sending troops to the Middle East, that means a majority of voters favored candidates opposed to the bill.

The election was held in Aichi Prefecture, home of Prime Minister Toshiki Kaifu. Kaifu campaigned in the district a week ago, making a pitch for his plan to create a Peace Cooperation Corps to be sent to the Middle East.

But after the election today, not even LDP spokesmen were willing to predict that the vote would make a difference in winning passage of the troop-dispatch bill. While the LDP holds a majority in the lower house of the Diet, the opposition still controls the upper house. Current wisdom holds that Kaifu's troop bill will likely be defeated, and polls show public opinion firmly against it.