The battle for Hougang comes down to a straight fight between businessman Png Eng Huat from the Workers' Party and Desmond Choo for the People's Action Party.
Both candidates successfully filed their candidacy papers at the nomination centre of Serangoon Junior College on Wednesday morning.
The supposed twist of potential surprise WP candidate Poh Lee Guan turned out to be much ado about nothing as he failed to turn up even though he had been issued a political donation certificate, a prerequisite for standing in the by-election.
The veteran WP member was later spotted drinking coffee at a coffeeshop opposite the nomination centre where he told reporters he was the "unofficial back-up".
This even though WP party chief Low Thia Kiang had earlier stated that there was no such reserve candidate.
Independent candidate and former WP member Zeng Guoyuan did provide for the day's drama when he turned up in traditional male Punjabi garb to file his papers.
However, his application was rejected after he was disqualified for verbally abusing a public servant in 2008.
But he vowed to be back for the 2016 election as an independent candidate.
"People want somebody who is independent. By coming in, I know who I stand for. I won't be stopped next time," he said.
Choo, accompanied by Education Minister Heng Swee Keat and National Development Minister Khaw Boon Wan, was the first to arrive at the nomination centre.
Png followed shortly after, alongside party chief Low Thia Kiang and Sylvia Lim.
Party supporters from both sides turned up in full force despite the sweltering heat to lend support to their respective candidates.
Madam Safiah Omar, a customer servicer officer, told Yahoo! Singapore she came down to support the PAP before her shift starts in the afternoon. She said her family is a PAP supporter and will continue doing so.
Meanwhile Sidek Mohammed Ali, a Hougang resident since 1990, said he came down to support the WP as he was confident the single-member constituency would stay in opposition hands.
Campaigning proper can now start with both candidates set to start their campaign walkabouts and rallies over the next nine days.
This will be the second time Choo will be contesting the single-member constituency. During last year's General Election in May, he lost to WP's Yaw Shin Leong after garnering 35.2 per cent of votes.
For Png, he contested in the East Coast group representation constituency (GRC) last May where he and his team obtained 45.17 per cent of votes.
Come next Saturday on the 26 May, close to 28,000 voters in Hougang will again go to the polls to decide their new MP after Yaw was expelled from the WP following rumours of extra-marital affairs in February.
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Thank you for joining our live coverage of Nomination Day. More reactions and follow-up to come. Campaigning now set to start for the next nine days until Polling Day next Saturday.
Png Eng Huat takes to the stage: "Voters of Hougang, thank you. Come 26th May, please send me to Parliament so that the Workers' Party can continue to be your voice." He also addresses supporters in Mandarin and Teochew to loud cheers.
Desmond Choo takes to the stage: "Residents of Hougang, you guys have been amazing! Thanks for your support. Thank you! we have served the residents hard." He also addresses PAP supporters in Mandarin.
Returning Officer Yam Ah Mee takes to the stage to formally announce the candidates.
Pritam Singh and Lee Li Lian rallying WP supporters.
Sweltering heat at Serangoon JC not dampening mood of both sets of supporters.
WP's Gerald Giam: WP supporters already standing by to book rally sites. Likely to be held on Sat, Mon and Wed
Both candidates have inspected each other's papers and no discrepancies have been found. Returning officer Yam Ah Mee expected on stage shortly to make formal announcement of the candidates.
Disqualified Zeng Guoyan: "People want somebody who is independent. By coming in, I know who I stand for. I won't be stopped next time." Blamed his pet parrot for his verbal abuse offence in 2008. He says he will still try for the 2016 election as an election candidate.
For Hougang residents, they have been without an MP since the Yaw Shin Leong scandal. What are Hougang residents looking for in their new MP?
This will be second time PAP's Desmond Choo will be contesting the Hougang SMC.
Both sets of supporters are making their way to the Serangoon JC field and are preparing to unfurl their banners and party flags.
Nomination has officially closed. By-election will be a straight fight between PAP's Desmond Choo and WP's Png Eng Huat.
Candidates will have one minute to address supporters after that.
Returning Officer Yam Ah Mee and "GE star" will be making the official announcement of the by-election candidates shortly after 1230pm.
Both Desmond Choo and Png Eng Huat are checking each other's papers that have been put up on a noticeboard.
More on Zeng Guoyan's disqualification. He has no proposer and seconder. Also DQ'ed to a past conviction in 2008 when he verbally abused a public servant.
Just minutes to go before nomination closes. Still no sign of wildcard WP member Poh Lee Guan.
Madam Safiah Omar, customer service and PAP supporter says she came down to support the PAP before her shift starts in the afternoon. Says her family is a PAP supporter and will continue doing so.
WP supporter overheard telling PAP supporters to "Watch out for a Ferrari on the way out! Later kena bang ah"
Both sets of supports chanting names of respective candidates loudly.
Woodlands PAP branch activist and taekwondo coach Tay Xiong Sheng tells our reporter he's there to support Desmond Choo. He says he's energetic, reliable and trustworthy. Tay re-scheduled his lessons for the day to show up at Nomination Centre because the by-elections are "once in a blue moon"
Independent candidate Zeng Guoyan has been disqualified as a candidate for a previous public offence of verbally abusing police officers at his shophouse.
WP chief Low Thia Kiang tells media he is not worried about WP unity but said he would deal with Poh Lee Guan later. He said he would answer any questions on Poh later but said the responsibility is on him to inform the party of his intentions.
Both approved candidates are now scrutinising each other's papers.
Desmond Choo's application to contest Hougang by-election has also been approved.
30 minutes to go before Nomination closes. Still no sign of WP's Poh Lee Guan
Nomination papers for WP's Png Eng Huat have been accepted, according to WP supporters on the ground.
Pritam Singh tells WP supporters not to boo when Desmond Choo makes his speech later.
So far, Desmond Choo, Png Eng Huat and Zeng Guoyan are inside the Nomination Centre to file their nomination papers. No sign of Poh Lee Guan yet.
PAP supporter tells our reporter: "I'm not part of Hougang but a few of us wanted to come because as you can see (points to WP supporters), they outnumber us"
National Development Minister Khaw Boon Wan also spotted, greeting PAP supporters.
Potential nominees have until 12pm to file their election papers. Official announcement of candidate list will be announced at 1230pm
Both sets of supporters engage in chanting match. WP supporters seems to be edging it.
No sign yet of surprise potential nominee of WP's Poh Lee Guan. WP supporters heard asking if anyone has seen him.
Wildcard Zeng Gouyan has been spotted arriving in a colourful outfit.
WP supporters appear to outnumber PAP supporters. Pritam Singh urges them to get louder.
WP candidate Png Eng Huat arrives, accompanied by party bigwigs Chen Show Mao and Faisal Abdul Manap
Not to be outdone, Workers' Party supporters are shouting "Huat ah" (in reference to nominee Png Eng Huat) and "Workers' Party" chants
PAP supporters are beginning to chant "PAP" and blowing horns.
Supporters from both PAP and WP are also making their way into the Nomination Centre. They are distributing their party flags but are not allowed to unfurl them yet.
1037AM: PAP candidate Desmond Choo, along with Education Minister Heng Swee Keat, arrives at Nomination Centre at Serangoon JC. Desmond says he is excited and hopes to be nominated succesfully.
Welcome to the live blogging coverage of Nomination Day for the Hougang by-election.
The emergence of Workers' Party veteran Dr Poh Lee Guan as a surprise potential nominee has added a fresh twist in what was supposed to a straight fight between WP's Png Eng Huat and People's Action Party's Desmond Choo.
Former WP member Zeng Guoyuan may also be a potential wildcard after he also collected election papers.
Join us at 1045am as we begin our live blogging coverage on events from nomination centre, Serangoon Junior College.