The pro-democrats suffered another defeat in eight months after Yiu Chung-yim narrowly lost to Vincent Cheng of the Democratic Alliance for the Betterment and Progress of Hong Kong (DAB) in the same constituency in the March by-election.

[4] The by-election of the Hong Kong Island, New Territories East, Architectural, Surveying, Planning and Landscape as well as Yau Wai-ching's Kowloon West seats was held on 11 March 2018.

However, in the March Kowloon West by-election, the pro-Beijing Democratic Alliance for the Betterment and Progress of Hong Kong (DAB) candidate Vincent Cheng made an upset victory by defeating pro-democrat Yiu Chung-yim.

[7] In late August, a 25-metre billboard of Chan Hoi-yan as a "health ambassador" outside Cross-Harbour Tunnel in Hung Hom funded by pro-Beijing Kowloon Federation of Associations (KFA) with an estimated cost of more than HK$248,000 sparked controversy the election rules dictate that candidates are only allowed to spend a maximum of HK$1.82 million on expenses while Chan had not yet declared herself as a candidate.

He cited her declaration in July 2016, made jointly with political party Demosisto and Eddie Chu, calling for "democratic self-determination" while keeping open the option for independence.

[13] Lee's platform focuses on four themes: fighting for democracy, better living, a stronger civil society and resisting the "mainlandisation" of Hong Kong, while Chan said she intended to put citizens' welfare above politics.

Fung focused on attacking the pro-democrats for its "undemocratic" mechanism of selecting the candidates for this election, claiming that it was the reason for him to eat his promise of not running again after he lost the March primary.