Initial polls recorded approval ratings as high as 70 % for the incumbent, Chen Shui-bian of the Democratic Progressive Party (DPP), which inevitably led to expectations that he would breeze through the election into a second term of office. However, the election heated up at the end of May when Ma Ying-jeou of the KMT announced his intention to run.
起初眾人預料，民進黨籍的現任市長陳水扁，施政滿意度高達百分之七十，應可輕易過關、獲選連任，但是在五月底國民黨籍的馬英九決定投入選戰之後，選情立即白熱化。