In 2011, all but one of the GRCs were contested. This time, with all the 16 GRCs seeing electoral fights, which are the ones to keep an eye on? The Straits Times narrows it down to those that will see clashes between the PAP and leading opposition party, the WP, as well as the GRC that will be contested for the first time.
EAST COAST GRC
Could this be the Aljunied GRC in this general election (GE), changing its hue from white to blue?
What is certain is that the fight in East Coast GRC will be the most closely watched, as the Workers' Party (WP) is likely to send its second "A" team - next in line to the "A" team that party chief Low Thia Khiang successfully led to victory in Aljunied GRC in 2011 - to the constituency.
In the last election, East Coast GRC saw the narrowest win for a GRC for the People's Action Party (PAP), with 54.8 per cent of the vote.
WP's Gerald Giam is expected to return and lead the team again, this time with an elevated profile after four years as a Non-Constituency MP. The three others are likely to be selected from among these four: sociologist Daniel Goh, law firm partner Dennis Tan, research and consultancy firm chief executive Leon Perera, and librarian Mohamed Fairoz Shariff.
They will be up against the PAP slate headed by Manpower Minister Lim Swee Say, who has said he wants to return to the GRC. In his corner: office-holders Mohamad Maliki Osman and Lee Yi Shyan, plus Microsoft Singapore managing director Jessica Tan.
There was a buzz last night as about 80 activists and volunteers gathered at Mr Lim's Bedok ward for a pow-wow on election logistics.
The stakes are high for the PAP. Said its youth wing branch chairman Leong Yi Xing: "We see ourselves as one of the lines of defence.
"Imagine if East Coast and Aljunied both go that way (to the WP), then it opens up the way for them in the eastern region.
"Just adjacent to us, we have Pasir Ris-Punggol GRC, a lot of the SMCs. If we can hold the ground here, at least we can act as a buffer between Aljunied and the rest."
The PAP incumbents have been cautious about publicly commenting on the challenge, with the usually affable Mr Lim telling The Straits Times he will respond only after his team is formally introduced tomorrow.
Similarly, WP chairman Sylvia Lim said yesterday it would not be making any comments as yet. The party will begin introducing its candidates today.
Another hint that the ruling party had taken stock of the challenge: Fengshan ward - viewed as the GRC's weakest link - has been hived off as a single-seat constituency. The GRC is now the smallest, with 99,015 electors.
How the battle may go will depend on which narrative appeals to the hearts and minds of the voters.
The PAP team has emphasised its hard work on the ground, with residents praising the slew of new and upgraded projects.
Even Mr Giam has chimed in with bouquets for his rival, Ms Tan, saying in a Facebook post that "Jessica's work at the local and town level is certainly something we look to emulate".
But, in an indication that the WP team will fight the battle at the national level, he added, a general election is "about more than just voting for a local MP".
"It's also about ensuring that the people have bargaining power to make the government more responsive to people's needs," he wrote, arguing that new measures to improve citizens' welfare were a result of the last GE.
The argument however may not be as effective as in 2011, when the WP put all its top guns in Aljunied GRC, placing the onus on the residents to ensure opposition representation in Parliament.
This time, all its seven MPs are defending their constituencies.
But with half of East Coast GRC's voters from public housing and the other half in private homes - a group that traditionally is more sympathetic to the opposition's argument for greater checks and balances, it is likely to be GE 2015's hottest ward.
MARINE PARADE GRC
In 2011, public attention here focused on two young women in opposing teams: National Solidarity Party's telegenic Nicole Seah and PAP's Tin Pei Ling who was caught backfooted in a party video.
In the end, the PAP garnered 56.6 per cent of votes, the second-lowest for a GRC. It was a shock result as the incumbent team was headed by Emeritus Senior Minister Goh Chok Tong while the NSP team was relatively unknown.
This time, both women are gone from the GRC. Ms Seah has quit politics while Ms Tin is contesting on her own in MacPherson.
But other changes have ensured the temperature in the GRC remains relatively high. One, Joo Chiat - which in 2011 saw the PAP win by a whisker of 388 votes, has been absorbed into the GRC.
But more significant is that the WP - the most credible opposition party - is taking the place of the NSP in challenging the incumbents.
The WP team is expected to comprise Non-Constituency MP Yee Jenn Jong, lawyer Terence Tan, chocolate factory owner Firuz Khan, corporate lawyer He Ting Ru, and wealth manager Dylan Ng.
Speaking at a residents' barbecue event last night, Mr Yee said he had asked the WP leadership to stay and contest in the area. "I asked for a committed team, which I got," he said.
Like in East Coast GRC, there will be no new faces in the PAP team. It is led by Social and Family Development Minister Tan Chuan-Jin, and includes ESM Goh, NTUC FairPrice head Seah Kian Peng, lawyer Edwin Tong and doctor Fatimah Lateef.
On whether the team expects a tougher contest with WP, Mr Seah would said: "We take every party that comes seriously."
TANJONG PAGAR GRC
There are many firsts for this GRC, which sprawls across Singapore's historic city centre.
For the first time, there will be no Lee Kuan Yew. The late founding prime minister had represented Tanjong Pagar - which became part of the GRC when it was formed in 1991 - since 1955.
For the first time, there will be a contest. The Singaporeans First party, founded by former presidential candidate Tan Jee Say, plans to send in a team.
Few expect the contenders to mount a real challenge. The party, established in May last year, has no track record.
There are also few local issues that have ignited - being smack dab in the city centre has meant that concerns like transport congestion are not as pressing here as at other constituencies.
While Serangoon Road - the site of the 2013 Little India riot - is now under the GRC, residents regard the incident as a one-off that will not sway their votes.
Of interest though would be the performance of the PAP team, to be led for the first time by fourth-generation leader Chan Chun Sing. The others include Senior Minister of State Indranee Rajah, surgeon Chia Shi-Lu, former public servant Joan Pereira and retired assistant police commissioner Melvin Yong.
People will also watch the contest for the extent to which the PAP may invoke Mr Lee's legacy, and how his death could affect voter behaviour.
Asked whether it could be a factor in how people cast their ballots, Mr Chan says: "We don't take our residents for granted and we don't think that people will vote for us just because of what Mr Lee has done... we as a team must continue to work hard to gain the trust of our people to show that we are here for the long haul."
Mr Tan says he believes the PAP team would hope that there is a "LKY factor" but adds: "Today's PAP is different from Mr Lee Kuan Yew's PAP of the early years.''
He said the "liberal influx'' of immigrants in recent years has affected social mobility.
MARSILING-YEW TEE GRC
New name, new candidates, a new GRC entirely.
Little wonder it has left some residents rather bewildered, wondering what plans are in store for them. As Mr Bryan Toh, 40, a shop assistant who lives in Yew Tee - formerly part of Chua Chu Kang GRC - puts it: "So what will happen? Will ongoing changes that are supposed to be happening in Chua Chu Kang exclude us now?"
When contacted, the co-anchor for the PAP team Lawrence Wong sought to calm nerves, saying that the new configuration allows MPs to give residents in the area more attention. "Otherwise, the Marsiling part will be just a small part of a big Sembawang GRC, and the Yew Tee part will be just a small part of a big Chua Chu Kang GRC," he said. "So, now Marsiling and Yew Tee together form one GRC with more MPs looking after the GRC, with a dedicated town council, with more services, more attention. I think that's something that will benefit residents."
The Minister for Culture, Community and Youth, as well as Speaker of Parliament Halimah Yacob are being parachuted in, joining two familiar faces Alex Yam and Ong Teng Koon.
Contesting the GRC is Singapore Democratic Party, led by Dr Chee Soon Juan. He could not be reached last night but had said the party sees the moving in of Mr Wong as a compliment and that the PAP is "taking us seriously".
Aljunied GRC, which made history in 2011, seems likely to remain in WP's hands.
The party, led by Mr Low, a businessman, has confirmed that its "A" team comprising himself, Ms Lim and Mr Pritam Singh, both lawyers, and full-time MPs Chen Show Mao and Muhamad Faisal Abdul Manap will stay on.
While there are hints the PAP will send in veteran MPs like four-term Yeo Guat Kwang to try to regain the GRC, they are unlikely to match up to the marque names of the WP team. It is also unclear how much traction the Aljunied-Hougang- Punggol East Town Council's troubled finances has with voters, even with the Auditor-General finding serious lapses in its financial statements.
Ms Lim and Mr Singh, who turned up at their constituency's town council office yesterday, declined to comment.
Additional reporting by Toh Yong Chuan, Walter Sim, Chong Zi Liang, Janice Heng, Choo Yun Ting and Goh Yan Han
This article was first published on August 26, 2015. Get a copy of The Straits Times or go to straitstimes.com for more stories.