SINGAPORE : Singapore may see its 15th by-election with the expulsion of Hougang MP Yaw Shin Leong from the Workers' Party (WP).
If it is called by Prime Minister Lee Hsien Loong, it will be the first by-election in exactly 20 years.
The last time Singaporeans went to the polls in a by-election was in 1992.
Then-Prime Minister Goh Chok Tong called for one in Marine Parade GRC, to inject new blood into the People's Action Party's (PAP) ranks.
Deputy Prime Minister Teo Chee Hean was introduced as a candidate to replace the outgoing Lim Chee Onn.
It was a four-cornered fight, with the Singapore Justice Party, Singapore Democratic Party and National Solidarity Party joining the fray.
The PAP won with 73 per cent of votes.
For single wards, the last time a by-election was held was in Anson in 1981.
This was after incumbent PAP MP Devan Nair resigned to become President.
It was a three-cornered fight between PAP's Pang Kim Hin, United People's Front's Harbans Singh, and WP's J B Jeyaretnam.
The WP won with 51 per cent of votes.
A by-election is held whenever a seat falls vacant and the Prime Minister has the full discretion when to call for one.
In recent years, the deaths of PAP MPs Dr Ong Chit Chung in 2008 and Dr Balaji Sadasivan in 2010 also fuelled talk of by-elections.
These did not take place.
PM Lee said then that a vacancy does not affect the mandate of the government nor its ability to deliver on programmes and promises.
He said this after Nominated MPs Thio Li-ann and Dr Loo Choon Yong filed a motion to fine-tune the electoral system, which was tabled after the death of Dr Ong in July 2008. The motion sought to make it mandatory for a by-election to be called for if a seat is vacated by a GRC member from a minority community, half or more elected GRC members, or a member of a single-member constituency.
Mr Lee had then said: "The vacancy does not affect the mandate of the government, nor its ability to deliver on its programmes and promises. The government's mandate continues to run until the next General Election is called, when the incumbent team will render account to the electorate."
Following Dr Balaji's death, Mr Lee said in an interview in September: "(There is) nothing automatic about calling for a by-election. We have discussed this many times. In Jurong, Dr Ong Chit Chung passed away, we have not called for a by-election, there are other MPs looking after the ward. In Ang Mo Kio GRC, there are six of us and the other five will help to look after Chengsan - Seletar ward. I see no difficulty."
But in the case of Hougang which is a single ward, observers said it is clear that a by-election needs to be held.
Under the law, the timing is up to the Prime Minister to decide.
Eugene Tan, assistant professor of law at Singapore Management University, said: "Here we have a situation where the constitution provides where a Member of Parliament...that his seat actually becomes vacant - if he either ceases to be a member, is expelled or resigned from the political party for which he stood in the election. So in this case, Mr Yaw was expelled by his party and so the seat of Hougang is now vacant.
"It is clear that a by-election has to be called, in this case, because the Parliamentary Election Act states that where there is a vacancy, the Prime Minister would then have to advise the President to issue a writ for election. The law is actually silent on how soon the by-election has to be called, but if we go by convention, then we would see that it will be within a reasonable time frame, and I think that would be between three and six months."