Su actively campaigned for the DPP presidential nomination in 2008, but finished second to Frank Hsieh. Su eventually teamed with Hsieh as the vice presidential nominee; the DPP lost to the Kuomintang ticket of Ma Ying-jeou and Vincent Siew. Su ran for Taipei City Mayor in November 2010, but lost to the incumbent Hau Lung-pin by a 12-point margin. Su campaigned for the 2012 presidential candidacy of the DPP in 2011, but lost to Tsai Ing-wen by a very narrow margin. Following the loss of Tsai to Ma Ying-jeou, Su was elected to succeed Tsai as DPP chairman in 2012.