太陽花學運
Su declared his candidacy for the 2012 presidential candidacy, but lost a DPP party primary held in April 2011 to Tsai Ing-wen and Hsu Hsin-liang, by a margin of 1.35 percent. He was subsequently elected DPP chairman in May 2012, and was succeeded by Tsai in 2014, after dropping out of the chairmanship election in the wake of the Sunflower Student Movement.