The three constituencies of Potong Pasir, Joo Chiat and East Coast GRC are held by the ruling party, but saw the fiercest contests in the 2011 polls. And despite reassurances that the Electoral Boundaries Review Committee bases its decisions largely on population changes, the fact that these were hot contest spots inevitably sparks speculation in some quarters that they might be redrawn this time.
At least two of the constituencies have demographic anomalies that would typically prompt redrawing in any case.
In the Potong Pasir Single-Member Constituency - where Mr Sitoh Yih Pin of the People's Action Party (PAP) won by less than 1 per cent of the votes cast - the 17,385-strong electorate is the smallest among all SMCs, and falls way below the 20,000 lower limit of voters each single-seat constituency should have.
Singapore Management University law don and former Nominated MP Eugene Tan says: "It's far too small in terms of voters when compared with other SMCs, which have about 25,000 voters on average. This means, relatively speaking, the MP has a lighter workload and the voters are 'over-repre-sented' in Parliament."
Until the 2011 General Election, Potong Pasir was the ward longest held by the opposition; its voters backed opposition veteran Chiam See Tong for 27 years.
At the 2011 GE, Mr Chiam took a leap and led a Singapore People's Party team to contest neighbouring Bishan-Toa Payoh GRC, while his wife Lina stood in Potong Pasir. Both of them lost.
During those 27 years, Potong Pasir's boundaries were left largely untouched. Indeed, the ruling party's Mr Sitoh hopes it will stay this way: "I'm hoping that we remain an SMC.
"From talking to Mrs Lina Chiam, I think she wants to come back. It'll be good if she's given another chance to contest, because the winning margin was only 0.72 per cent."
Since that razor-thin win in 2011, Mr Sitoh has expressed his desire to further prove himself in the ward, and winning it again would certainly do that.
But analysts doubt the status quo will remain.
What is more likely to happen, they say, is that the constituency will be absorbed by Bishan-Toa Payoh GRC, so as to rebalance the population numbers.
It is also possible that a section of this newly combined GRC is then carved out to form a new single-seat constituency.
In Joo Chiat, another single-seat constituency, PAP MP Charles Chong beat his Workers' Party (WP) challenger Yee Jenn Jong by a 2.04 per cent margin in 2011.
What makes Joo Chiat an anomaly is its housing mix. It is the only constituency without a block of Housing Board flats in its midst.
That it will be left alone, being so unrepresentative of the general populace, is "almost unthinkable", says National University of Singapore political scientist Bilveer Singh.
He adds: "The Government has a habit of mixing private estates with public housing estates."
Speculation about boundary changes also swirls because of talk about Mr Chong's possible retirement from politics, and who would replace him.
Having served six terms, the veteran MP is widely expected to step down. New face Louis Ng, chief executive of the Animal Concerns Research and Education Society, has been tipped by some to replace Mr Chong in the ward, and has been active in the area.
Meanwhile, Mr Yee, now a Non-Constituency MP (NCMP) , is expected to contest there again.
With 22,752 voters, Joo Chiat can afford to grow bigger, and the boundaries committee could boost its size by including parts of neighbouring Marine Parade division, where there are public housing flats.
As for East Coast GRC, some also wonder if the WP's strong showing there in 2011 - winning 45.17 per cent of valid votes - would make it a candidate for boundary changes. The strong results led to one member of the WP team - Mr Gerald Giam - becoming an NCMP, which is offered to the top losers from the opposition.
But East Coast GRC is unlikely to be altered much.
Analysts tell Insight that the review committee might want to avoid appearing unfair. Says Prof Tan: "The east and north-east parts are made complicated because of the strong WP presence. The committee might keep changes to a minimum there to avoid accusations of major boundary changes as gerrymandering."
Additionally, the voter population of the area has barely grown since 2011 - from 120,207 to to 122,382. The area is also already very built-up, which means its population may not change much in the coming years.
This article was first published on July 19, 2015.
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