 Chen then served the Taipei City Government and mayor Chen Shui-bian in multiple positions, until joining the ROC Presidential Office in 2000, where he continued advising Chen Shui-bian.Chen was expelled from the Kuomintang on 2 December 1992, after becoming increasingly critical of party leaders.His expulsion from the party happened in the midst of a legislative election, but occurred too late for the KMT to officially pull their support of him.