In August,
Chan Hoi-yan, a former news anchor and political assistant to
Secretary for Food and Health Ko Wing-man emerged as a potential candidate for the pro-Beijing camp after Ko announced he would not run in the by-election.
Frederick Fung, a veteran pro-democracy legislator announced his candidacy after long speculations that he would run, and cited that he was unhappy the camp had decided on another veteran,
Lee Cheuk-yan, as Lau's backup, in case of disqualification of the candidacy of
Lau Siu-lai, one of the six ousted pro-democracy legislator in the
2016 oath-taking controversy who was commonly backed by the pro-democracy camp. Fung previously lost in the pro-democracy primary in the
March by-election to
Yiu Chung-yim and subsequently quit the
Association for Democracy and People's Livelihood (ADPL), in what was seen as a move for him to run as an independent in the by-election. Fung said he ran because he opposed the pro-democrats for monopolising the candidacy selection process. Political observer Dr
Chung Kim-wah said Fung's decision had caused uncertainty for the pro-democrat campaign would easily attract thousands of votes from the pro-democracy voter base that would cost pro-democrats the election. On 12 October, Lau Siu-lai's candidacy was invalidated by Returning Officer Franco Kwok Wai-fun as he claimed that Lau did not accept China's sovereignty over Hong Kong. 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. He said Lau had been "consistently holding the same political stance" and "had not taken any step to dissociate herself from such political stance until very recently". Lau accused Kwok's decision as "unreasonable" and her political views from 2016 were "completely twisted". Foreseeing the disqualification,
Labour Party veteran Lee Cheuk-yan signed up for the race as a "plan B". Chan also relied on the high popularity of former Secretary for Food and Health Ko Wing-man to sway swing votes, while Lee, learning from the defeat in March, struck a better balance between online and on-the-ground campaigns as the March pro-democracy candidate Yiu Chung-yim was criticised for focusing too much on online campaigns. He also highlighted his crucial goal of preventing a pro-Beijing dominance in the geographical constituencies, which meant the pro-democracy would lose the veto power against pro-Beijing attempts of changing the Rules of Procedure of the Legislative Council if they gained one more seats over the pro-democrats. 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. He received a lot of attacks from the pro-democracy figures who rejected him for being a pro-democrat and accused him for being a "
vote splitting tool" for Beijing. Fung reiterated by filing complaints to
Independent Commission Against Corruption (ICAC) against pro-democracy media for some of their accusations. ==Polling==