The People's Action Party (PAP) held on to the Bukit Batok seat, with its candidate Murali Pillai securing 61.2 per cent of the vote, against the 38.8 per cent share of his rival, Singapore Democratic Party (SDP) chief Chee Soon Juan.
The result for the PAP was 11.8 points lower than the 73 per cent achieved by the constituency's former MP David Ong at the General Election just eight months ago, where the PAP scored a landslide victory with a vote share of 69.9 per cent.
Still, it is a significant win, which saw the PAP retaining a single seat in a by-election for the first time in 37 years, and with a minority-race candidate.
The victory last night also broke its streak of having lost the last two by-elections - Hougang and Punggol East - held in recent times.
After the final result was announced at 11.30pm last night, Mr Murali thanked Dr Chee and the SDP for running a well-organised campaign, which gave him the opportunity to pitch his plans to voters in the ward, he said.
PM LEE'S MESSAGE
Congratulations to Murali Pillai on his win! Thank you, Bukit Batok voters, for your strong support. You have chosen an MP who is committed, trustworthy, and will go the extra mile for you.
Murali and his team have campaigned hard, but now their real work begins. He has served faithfully in Bukit Batok for many years, and with your support, will serve residents for many more.
Thank you to all the activists and volunteers who helped Murali campaign. This is not just a win for Bukit Batok, but shows all Singaporeans, and others too, that the Government and people are united in building a better nation together.
PRIME MINISTER LEE HSIEN LOONG, who posted this message on Facebook shortly after the victory of People's Action Party's Mr Murali Pillai was announced last night.
Dr Chee, in turn, congratulated his opponent while addressing his supporters at Bukit Gombak Stadium.
At a press conference in the PAP branch office, Mr Murali, 48, said he was humbled and encouraged by the results and pledged to start on his agenda for the constituency "tomorrow".
He dedicated his victory to Bukit Batok residents, saying: "This forms my statement of whom I'm serving and why I'm serving.''
Asked about his margin of victory, he said: "Coming from Aljunied, I'm used to razor-thin margins''.
He was in the PAP team that got 49 per cent of the vote in Aljunied GRC at last year's General Election.
For Dr Chee, 53, the defeat was his fifth, but supporters took consolation in the fact that it was also his best electoral showing since 1992.
He told his supporters: "I am so touched. I am so honoured. This doesn't quite feel like a defeat."
Although he did not win, he did better than SDP candidate Sadasivam Veriyah, who got 26.4 per cent of the votes in last year's General Election in a three-way fight.
Dr Chee told reporters he was "very disappointed" he did not "meet the 50 per cent threshold", but pledged to stay on in Bukit Batok to fight for their votes.
The contest had been billed as a tough one by the PAP from the start, given the damaging circumstances that triggered it. In March, Mr Ong had resigned over an alleged extramarital affair, the second PAP MP to do so in four years.
There was also the by-election effect, which Minister for Culture, Community and Youth Grace Fu alluded to last night. She said: "During a by-election, it's always difficult to gauge how voters will vote and we like to think that this is a strong mandate."
Prime Minister Lee Hsien Loong, in a Facebook note last night, thanked Bukit Batok voters for their "strong support".
Deputy Prime Minister Tharman Shanmugaratnam told reporters: "To my mind, he came out stronger than I expected. He did exceptionally well."
Analysts said it was a clear win for the ruling party, despite the vote swing being larger than the 10.8 percentage point in the 2013 Punggol East by-election.
They said the PAP's results in last year's polls had been boosted by the country's 50th birthday celebrations and the emotions brought on by the death of founding Prime Minister Lee Kuan Yew.
Some observers also pointed to race as a possible factor contributing to the swing, although it was unclear to what extent this shaped the outcome.
UniSIM College senior lecturer Walter Theseira said: "I think most Singaporeans don't vote on race but we would be hopelessly idealistic to think it played no part at all."
Political watchers said Dr Chee's performance was also a sign that questions about his character, raised by some PAP leaders during the campaign, might have caused some voters to think twice about him, although others felt that it could have turned some voters off.
Looking ahead, Mr Murali said his focus will now be on residents and rolling out his "ambitious agenda" for the constituency.
"There is a lot of work to be done and I will start tomorrow. Let me say again that I will serve everybody, irrespective of their political affiliation," he said.
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