More multi-cornered contests could feature in the next general election with several constituencies already claimed by more than one opposition party.
And despite these overlapping claims, several party leaders have said they will stand their ground.
Among those eyed by more than one party are Tanjong Pagar, Tampines, Marine Parade, Pasir Ris-Punggol and Bishan-Toa Payoh GRCs; and the single seats of Whampoa, Mountbatten and Potong Pasir.
This puts all eight active opposition parties - the Workers' Party (WP), Democratic Progressive Party (DPP), National Solidarity Party (NSP), Reform Party (RP), Singapore Democratic Alliance (SDA), Singapore Democratic Party (SDP), Singapore First Party (SingFirst) and Singapore People's Party (SPP) - potentially on a collision course if they do not reach a compromise.
For instance, up to four parties - the DPP, RP, SDP and SingFirst - have indicated interest in or held walkabouts in Tanjong Pagar GRC.
Party leaders told The Sunday Times that while they will not deliberately initiate three-cornered fights, they will not go out of their way to avoid one either. But it has become harder to avoid competing in the same areas given several high-profile defections from parties since the 2011 General Election.
DPP secretary-general Benjamin Pwee, for example, was in the SPP team that contested in Bishan-Toa Payoh GRC in 2011. He quit the party a year later. He now intends to contest the GRC on a DPP ticket, and deploy someone to Potong Pasir - which was held by his former mentor and SPP chief Chiam See Tong for 27 years. If Mr Pwee's DPP does pick Potong Pasir, it could be taking on Mrs Lina Chiam, who lost narrowly in 2011 to the People's Action Party's Mr Sitoh Yih Pin.
NSP president Sebastian Teo said his party will not shrink from places where it has been working the ground. These include Tampines and Marine Parade GRCs and the single seats of Whampoa and Mountbatten. "We are not scared of three-cornered fights," he said.
But he disclosed that he has vetoed some members' requests that NSP contest Potong Pasir, and Moulmein-Kallang GRC - where the WP fielded a team in 2011.
Mr Goh Meng Seng, who applied in May to register his People's Power Party, has his sights on Tampines GRC. He contested there in 2011 when he was with the NSP.
SDA chief Desmond Lim said his party will definitely field a team in Pasir Ris-Punggol GRC, where it contested in 2006 and 2011. SingFirst - launched in May last year - is also staking claim to the GRC.
Mr Lim said: "We've never stopped our activities there, and continue to work the ground and serve the people wholeheartedly. We won't speculate as to which party is coming (to our turf) or not."
Opposition party leaders took pains previously to call for unity.
But they say they are less worried about the vote being split after the seminal Punggol East by-election in 2013. The outcome put paid to the conventional wisdom that a multi-cornered contest would disadvantage the opposition. In a four-cornered fight, the WP won with 54.5 per cent of votes cast. The SDA and RP candidates won less than 2 per cent of votes combined.
Said Mr Pwee: "It's not a multi- cornered fight just because more than two parties run. It's a fight only when voters see three or more credible candidates."
But jockeying for a constituency may be moot if it no longer exists once new electoral boundaries are released - a point noted by SingFirst secretary-general Tan Jee Say. "We can't talk seriously when the boundaries are not known. We want to avoid multi-cornered fights. But what happens if a GRC is split two or three ways?" Still, he is hopeful "goodwill will prevail" before polls in the opposition camp.
Chong Zi Liang and Tham Yuen-C