In the September 1963 elections in Singapore, Tan Jing Quee contested as a Barisan Sosialis candidate against the PAP Minister for Culture S. Rajaratnam at Kampong Glam. Tan lost narrowly by 220 votes, conceded the fight and shook Rajaratnam's hand. The following month, as Assistant Secretary-General of the left-wing Singapore Association of Trade Unions (SATU), Tan helped organise a two-day protest strike against the move of the Registrar of Trade Unions to deregister the association for alleged “communist front activities”. The SATU comprised seven major left-wing unions in Singapore, including the Singapore General Employees’ Union, and formed a crucial mass base for the Barisan. After planning for the strike, Tan was arrested under Operation Pecah in the early hours of the morning, before the protest was scheduled to start. Also detained were other trade union leaders and several Barisan candidates in the September elections, three of whom had been successful at the polls. Pecah followed Operation Coldstore, a much larger crackdown launched earlier on 2 February in the same year, which had broken the back of the Singapore left. In a poem titled, simply, “Fajar”, Tan wrote about how and when he was arrested in September:

The other historical “Fajar” was of course the arrests of the eight members of the organ's editorial board a decade ago. The incarcerations which broke the left-wing movement in February and September 1963 signified a new phase of Singapore's history.