THE prestige of the ruling Kuomintang and the political future of one of its brightest stars is on the line in a bitter fight for central Taiwan's Chiayi City. Former Mainland Affairs Council chairman Vincent Siew is trying to capture the city's single seat in the Legislative Yuan from incumbent Tsai Tung-jung, of the pro-independence Democratic Progressive Party (DPP), in Saturday's election. Chiayi City is the only constituency in which there is a direct face-off between the Kuomintang and the main opposition party. In his campaign, Mr Siew noted his long government service and high international profile, highlighting the benefits for Chiayi voters in having a strong leader in the legislature. Meanwhile, Mr Tsai focused on his support for a plebiscite on Taiwan's future and his long activism in the grassroots opposition movement. The chairman of the Association for a Plebiscite in Taiwan, Mr Tsai claims Mr Siew will be swallowed up in the Kuomintang's legislative voting bloc if elected, and is pushing a 'double-win' strategy for Chiayi by keeping Mr Siew in the central government and himself in the legislature. Mr Siew resigned from his Mainland Affairs Council post last Friday to show he intends to 'fight with my back against the wall' and to undercut Mr Tsai's claim. Law professor Hsu Ching-hsiung, of Tamkang University, believes President Lee Teng-hui drafted Mr Siew to run to find out if the Kuomintang could win in a one-on-one contest and to give his protege a popular mandate. If Mr Siew 'recovers' the Chiayi City seat, he is likely to be rewarded with a high party post and may be put on the fast track to run for Taiwan provincial governor in 1998 and even for eventual nomination as premier, sources said. Even if Mr Siew loses, the former Economic Affairs Minister and chief of the Council for Economic Planning 'will return in a good post after next March's presidential election', said Professor Hsu. Kuomintang sources say Mr Siew leads by up to five percentage points, but a DPP leader said, 'if you asked me about Tsai's chances 20 days ago, I'd have to say he'd lose, but now it's a 50-50 race'.