On Tuesday night, Ms Raeesah Khan resigned from the Workers' Party and Parliament, which removes her from her role as an MP for Sengkang GRC.
What happens next? The Straits Times explains.
1 WHAT HAPPENS IN SENGKANG GRC? WILL THERE BE A BY-ELECTION?
It is unclear.
In 2017, when President Halimah Yacob, who was then an MP for Marsiling-Yew Tee GRC, resigned from her parliamentary seat to contest the presidential election, there was no by-election called.
Replying to a query from Aljunied GRC MP Pritam Singh in Parliament earlier that year, then Minister in the Prime Minister's Office Chan Chun Sing said there is no need to hold a by-election for a GRC if a member of the team resigns.
It is possible that the rest of the Sengkang GRC team - Ms He Ting Ru, Associate Professor Jamus Lim and Mr Louis Chua - could step down from their seats, triggering a by-election.
By-elections have been held 13 times since Singapore's independence, the last being held in 2016 to fill a vacancy arising in Bukit Batok SMC.
2 WHAT DOES THE LAW SAY ABOUT BY-ELECTIONS?
The Parliamentary Elections Act states that a Writ of Election shall be issued only if all the MPs for the GRC have vacated their seats. If only one of the MPs vacates his or her seat, the needs of residents in the GRC would continue to be served by the remaining members of the GRC team.
In 2019, Singapore's apex court dismissed an appeal for the remaining three MPs in Marsiling-Yew Tee GRC to vacate their seats and for a by-election to be called in the constituency following Madam Halimah's resignation as an MP in 2017.
Referencing the relevant parliamentary debates in 1988, the Court of Appeal said it is clear that Parliament had decided there would be no obligation on the Government to call a by-election in a GRC when a single vacancy arises.
This arrangement, it was decided then, was preferable to the alternative - of the possibility that one member of a GRC team could hold the other members of the team to ransom.
In the case where the vacancy was previously filled by a minority member and minority representation in Parliament would be diminished if the seat was left unfilled, the court said that Parliament had decided that this risk was an acceptable trade-off for preventing the situation of an MP holding other members of the team to ransom.
3 WERE THERE OTHER OCCASIONS WHEN MPs VACATED THEIR SEATS AND WHAT HAPPENED?
In 2016, then People's Action Party (PAP) MP for Bukit Batok David Ong resigned over a personal indiscretion, triggering a by-election for the single seat.
Mr Murali Pillai of the PAP won against the Singapore Democratic Party's Dr Chee Soon Juan with 61.2 per cent of the vote.
In 2012, then Speaker of Parliament and PAP MP Michael Palmer resigned from his Punggol East single seat after admitting to an extramarital affair.
The subsequent by-election in January 2013 saw a four-way fight that Ms Lee Li Lian of the WP won with 54.5 per cent of the vote. She lost it to PAP veteran Charles Chong in the 2015 General Election, and the constituency was redrawn into Sengkang GRC ahead of the 2020 election.
Also in 2012, Hougang MP Yaw Shin Leong was expelled from the WP following allegations of extramarital affairs. The party said he had failed to uphold transparency and accountability. The by-election then saw WP's Mr Png Eng Huat defeat PAP's Mr Desmond Choo with 62.1 per cent of the vote.
In 2008, Jurong GRC MP Ong Chit Chung died suddenly at home of a heart attack at age 59. A debate ensued on whether there was a need to call a by-election. The seat was left vacant until the next general election in 2011.
