After a temporary period of research at the
London School of Economics in England, Chen was appointed the deputy secretary-general of the Presidential Office in February 2007. His appointment drew mixed reactions, with the support from the DPP legislative caucus and opposition from the
Kuomintang legislative caucus. Chen served with
Lin Chia-lung, former director of the
Government Information Office. After the
DPP chairmanship election in May 2008, chairwoman-elect
Tsai Ing-wen announced the appointment of Chen as the deputy secretary-general of the party. He held the position with Cho Jung-tai until 2009. Chen is now concurrently serving as both the spokesperson of the
Democratic Progressive Party and the chief executive officer of the party's Policy Research and Coordinating Committee since May 2011. In the
2012 legislative elections, Chen was placed on the DPP electoral list, from which 13 members were elected based on the number of votes the DPP received. Being the eighth member on the list, Chen returned to the Legislative Yuan once again as a legislator in February 2012. He was reelected via proportional representation in 2016. Chen faced fellow lawmakers
Chao Tien-lin,
Lin Tai-hua, and
Kuan Bi-ling in a Kaohsiung mayoral primary held in March 2018, and was named the Democratic Progressive Party candidate for the mayoralty. On November 24, 2018, he was defeated by
Han Kuo-yu, the
Kuomintang mayoral nominee, by more than 150,000 votes. Chen became the first DPP mayoral candidate to lose in the
special municipality of Kaohsiung, established in 2010. His defeat marked the end of 20 years of
Democratic Progressive Party governance in the old city area of
Kaohsiung, and 33 years of governance in the old
Kaohsiung County area. Chen's resignation from the vice premiership took effect on 19 June 2020, as he then represented the DPP as their candidate contesting in the
2020 Kaohsiung mayoral by-election scheduled for 15 August. ==Return to mayoralty==