The People's Action Party (PAP) has named its candidates for all but two of the 13 single-seat constituencies at stake in the Sept 11 General Election - Fengshan and Punggol East.

It is perhaps the surest sign that the two are likely to be hot seats to watch.

In the PAP line-up for single-member constituencies (SMCs) this time around are two Members of Parliament going solo for the first time and an election newbie.

The opposition parties, meanwhile, have mostly not revealed who they will field. But they have at least indicated where they will run, and it looks like all SMCs will see a contest.

Two - MacPherson and Potong Pasir - look set for multi-cornered fights, with several parties and independents expressing interest.

The Straits Times picks out the SMCs to watch this year.

FENGSHAN

Why Fengshan was carved out of East Coast GRC has been a much discussed topic in the past month since the electoral boundaries report was released.

One popular theory is that the ward polled poorly for the PAP in the 2011 General Election, affecting the party's overall result in East Coast GRC, so hiving it off would protect the GRC for the PAP.

It does not help that the SMC, with 23,404 voters, sits awkwardly among the four wards of East Coast GRC, much like the hole of a donut.

While all that may be speculation, the pundits generally agree that Fengshan will see a tough fight.

The secrecy surrounding the PAP and Workers' Party (WP) candidates there suggests the parties think so too.

Incumbent MP Raymond Lim has said he is retiring from politics, but the PAP has given few hints about who it will field there. This is a departure from its practice this time round in most other SMCs, where it has introduced its candidates.

A name bandied about initially, of grassroots volunteer Cheryl Chan, 38, raised questions about the PAP's strategy for Fengshan. The ruling party has rarely fielded a new face in an SMC and talk of her candidacy seemed to suggest that the party was preparing to "give up" on Fengshan.

Meanwhile, the WP has also put up smoke screens of its own.

Although it made clear early that it would be contesting Fengshan, it has been tight-lipped about its candidate. In a move that has kept even voters there guessing, the WP has sent its entire East Coast GRC team to walk the ground in Fengshan with its potential candidate.

WP chairman Sylvia Lim, 50, sparked talk when she posted a picture of herself online and talked about the "heavenly" taste of Fengshan. For a few days, speculation swirled that she might be fielded there, but then she announced she would remain with the rest of the WP team in Aljunied GRC.

So far, WP members spotted in Fengshan include Non-Constituency MP Gerald Giam, 37, and new faces Dennis Tan, 44, Daniel Goh, 42, Leon Pereira, 44, and Mohamed Fairoz Shariff, 36. Sources close to the party said that until very recently, party leaders have been undecided about who to field. But Mr Tan and Dr Goh are possible contenders.

The WP will be introducing its candidates from today.

Manpower Minister Lim Swee Say, who will helm the PAP's East Coast GRC team, has said the party will unveil its Fengshan candidate tomorrow.

MACPHERSON

For weeks now, MacPherson SMC has become the scene of a hot battle between the WP and the National Solidary Party (NSP). They have disagreed over who should contest and it looks like both will do so, causing a three-cornered fight that will split the opposition vote.

The SMC is not the only one likely to see a three-way fight - Potong Pasir too could see one if an independant enters the fray - but it is likely to be the only one where two opposition parties will clash.

It all started with the WP staking a claim on the SMC the week electoral boundaries were revealed. The move was seen by some as the WP encroaching on NSP's turf. The NSP had contested Marine Parade GRC in 2011 when MacPherson was part of the GRC.

At first the NSP backed off in the name of opposition unity. But it made a U-turn last week, saying it would contest there after all. The move set off a series of resignations within the NSP, which analysts feel may have all but wrecked the party's chances there.

While the WP has not revealed its candidate, The Straits Times understands it could field Mr Bernard Chen, 29, a project executive at Ang Chin Moh funeral services.

The new faces, meanwhile, will face incumbent MP Tin Pei Ling, 31, who will be going solo in an election for the first time.

The first-term MP has been working the ground for the past four years and says she is familiar with the issues that residents face. She will be aided by an experienced MacPherson PAP branch.

The constituency was contested six times as a single seat with the PAP winning more than 65 per cent of the vote each time. Even as part of Marine Parade GRC in the last election, it reportedly garnered the second-highest PAP vote share among the wards in the GRC.

Said Ms Tin: "We have been here for the past four years and what drives us is really the desire to make a positive impact on the lives of people in MacPherson. So whether it is one or two or however many parties coming to contest, our residents' interests will remain our top priority."

POTONG PASIR

It was among the constituencies where the PAP won by the lowest margin - Mr Sitoh Yih Pin won by less than 1 per cent of the votes cast.

Until the 2011 General Election, Potong Pasir was the ward held longest by the opposition, with its voters having backed opposition veteran Chiam See Tong for 27 years.

In the last election, his wife Lina stood in Potong Pasir, while Mr Chiam led the Singapore People's Party team which lost in neigbouring Bishan-Toa Payoh GRC.

Mrs Chiam, 66, has said she will be back again at the SMC. She has been seen on walkabouts in the area with Mr Chiam, and observers expect nostalgia for the opposition veteran to help boost her votes. This time around, Mr Chiam is unlikely to contest the elections.

Mr Sitoh, 51, is expecting a tough fight, but asked to be fielded there again to prove himself.

He says: "I only ask Potong Pasir residents to judge me for what I have done, can do and will continue to do for them... We can only build and rebuild our relationship with Potong Pasir residents by showing them that we make promises and we deliver. Consistency is the best preparation for the elections."

A third candidate is likely to be independent Tan Lam Siong. The former NSP secretary-general, who quit the party in June after barely four months in the post, is determined to fight in Potong Pasir.

Seen doing house visits last night, he said: "I am firm in my decision."

MOUNTBATTEN

Opposition politician Jeannette Chong-Aruldoss, 52, has weathered many changes in the past year - losing her position as secretary-general of the NSP, then quitting to join the Singapore People's Party (SPP).

But the one constant is her desire to contest Mountbatten SMC.

Mrs Chong-Aruldoss, who stood there in 2011, will be back for a rematch with the PAP's Lim Biow Chuan, who won in the last election with 58 per cent of valid votes.

Although Mrs Chong-Aruldoss will be contesting under the SPP banner this time, she has been running her campaign rather independently, with her own helpers instead of SPP members supporting her.

In the recent week, she has also aligned herself with WP, speaking out against the ruling party for bringing up issues about the WP's town council, and inviting WP Non-Constituency MP Yee Jenn Jong to her condominium for a BBQ to meet residents.

It could give a clue about the issues she will bring up during campaigning, since Mr Lim is the chairman of the Marine Parade-Mountbatten Town Council.

But Mrs Chong-Aruldoss said: "The role I want to play is to help the government do its job better... there is a broader picture of accountability and transparency, checks and balances and helping the government think through their policies better."

Meanwhile, Mr Lim says national issues such as housing, transport and population issues will be his focus, but adds that he has not started campaigning proper.

"We have not gone out with the PAP badge to do any campaigning for votes. I know my opponent has been, but there's a way to do things and I don't agree with the way she has done it. I think she has been campaigning already," he said.

PUNGGOL EAST

On one side is the WP's Ms Lee Li Lian, 37, the incumbent ready to defend her Punggol East SMC seat.

She became MP in a by-election in 2013, after former Speaker of Parliament Michael Palmer of the PAP stepped down over an extra-marital affair.

On the other side? It looks like it will be six-term MP Charles Chong, 62, of the PAP.

Until recently, many had wondered who the PAP would field in the constituency, one of the fastest growing with 34,410 voters. But Mr Chong's appearance at the constituency's National Day dinner earlier this month all but confirmed his candidacy.

Many had expected him to retire from politics, and his entering the fray at Punggol East has raised eyebrows. Some have even characterised the PAP's decision to field him as a "suicide mission".

But Mr Chong is a familiar face, as some areas of the ward were under his purview when he was an MP in Pasir Ris-Punggol GRC from 2001 to 2011.

Observers also say it is hard to gauge support for Ms Lee, who has not served a full term.

While Mr Chong has called her a "nice person" who "speaks up for mothers", he says the residents of Punggol East have been short-changed and are getting "a raw deal".

"When we handed it over to WP, it was still part of Pasir Ris Punggol GRC town council. It had a surplus then.

"At the new town council, the finances look to be mismanaged. Should Punggol East continue to subsidise Aljunied? I dont think so," he said referring to the financial and governance lapses uncovered at the WP-run Aljunied-Hougang-Punggol East Town Council.