In the March 2018 Legislative Council by-election triggered by the disqualification of Youngspiration's Yau Wai-ching over the oath-taking controversy, the DAB supported its member Vincent Cheng and the former FTU legislator Tang Ka-piu who joined the DAB before the election to run in Kowloon West and New Territories East respectively. Despite Tang's loss, Cheng made a surprising upset by narrowly defeating independent democrat Yiu Chung-yim, making it the first time the pro-Beijing camp received greater vote share than the pro-democrats in a geographical constituency since 2000 and the first time a pro-Beijing candidate won in a geographical constituency by-election since 1992.