One jogged into the venue, shaking hands and exchanging high-fives with his cheering and whistling supporters.
The other strolled in with his wife, smiling as he waved at supporters.
In the end, it will be a straight fight between the People's Action Party (PAP) and the Singapore Democratic Party (SDP), and both candidates appeared relaxed even as they prepare to battle for the Bukit Batok single-member constituency (SMC).
Lawyer Murali Pillai, 48, who was in jogging shoes, was all smiles as he greeted PAP supporters.
Deputy Prime Minister Tharman Shanmugaratnam and Senior Minister of State for Home Affairs and National Development Desmond Lee, both MPs in Jurong GRC, were also present to show their support.
Following them was a long train of supporters dressed in PAP white.
SDP chief Chee Soon Juan, 53, appeared just as relaxed as he strolled in with his wife, Dr Huang Chih-Mei.
A small but vocal group of "red" supporters were close by, armed with clappers, umbrellas and flags.
Some prominent figures were spotted among the supporters who turned up at the nomination centre.
Former PAP MP Lim Boon Heng, who was there to show his support for Mr Murali, said: "If I were a resident in Bukit Batok and I have to vote in this by-election, I'll be looking for somebody whom I feel is sincere and genuinely wants to serve the people."
Former independent candidate Han Hui Hui, dressed in her trademark attire of polo shirt and jeans, was standing with SDP supporters. The blogger said she was there to listen to the candidates' speeches.
"Hopefully their speeches will include that they will fight for issues like justice, transparency and accountability," she added.
Dr Huang was popular among the SDP supporters and many wanted to have their photos taken with her.
But the housewife said the Nomination Day was just another ordinary day for her family.
Dressed in a red tank top, she said with a smile: "I just make sure our household remains as normal as possible. I don't think the kids are aware that today is Nomination Day."
As Dr Chee later commented at a press conference at Keming Primary School's canteen, the nomination process had been "uneventful".
Two other hopefuls, Mr Shirwin Eu, 32, and veteran opposition member Kwan Yue Keng, 66, hardly caused a stir with their appearance.
Mr Kwan, an SDP candidate for Bukit Batok in 1988 and 1991, said he was a "stand-in candidate" in the event that Dr Chee is disqualified.
"I'm here to prevent a walkover," said Mr Kwan, who was carrying a briefcase with a stack of papers.
He added that he still has a core group of supporters in Bukit Batok.
Mr Eu and Mr Kwan eventually left without filing any nomination papers after election officials explained to them the requirements and procedure under the law for nomination as an election candidate.
A drizzle began when Mr Murali and Dr Chee started to give their speeches.
Mr Murali addressed his supporters amid chants of "Ah Mu", a nickname he earned in the constituency.
He spoke in four languages and called on them to help make Bukit Batok "a beautiful place for all of us".
Dr Chee's speech was cut after a minute - the time allocated for each speech - but he managed to end with a promise to residents that he would make Bukit Batok the envy of Singapore.
The 25,727 voters of Bukit Batok SMC will go to the polls on May 7. Their previous MP, Mr David Ong, resigned in March over an alleged affair.
Over the next nine days, the two candidates are expected to canvass the ground and speak at rallies.
Police have announced two rally sites: Bukit Batok Industrial Park and Bukit Gombak Stadium.
There will be no rallies today.