A former mayor running without the support of any political party on Sunday defeated by a slim margin the incumbent governor of Tochigi Prefecture who had the backing of all major parties but the Communists.

The victory of Akio Fukuda in the Tochigi race, together with that of writer Yasuo Tanaka in the Nagano gubernatorial election in October, appears to indicate that traditionally conservative rural politics in Japan have been made unpredictable by the growing power of unaffiliated voters.

Fukuda, 52, the former mayor of Imaichi in the prefecture, collected 336,161 votes, only 875 more than the 335,286 votes for Gov. Fumio Watanabe, 71, dashing the incumbent's hopes of winning his fifth four-year term of office, final returns show.

Former prefectural official Kaname Noguchi, 59, backed by the Japanese Communist Party, came in a distant third with 34,009 votes. All three candidates were independents.