Another by-election so soon after a general election. It is a situation the People's Action Party does not relish - it lost two such contests within two years of the 2011 General Election.
The by-elections in Hougang in 2012 and Punggol East in 2013 were triggered by the incumbent MPs - one from the Workers' Party and one from the PAP - vacating their seats after extramarital affairs.
The by-elections, both won by the WP, also came after a heated general election in 2011 that saw the PAP's share of the popular vote dip to its lowest since independence.
This time round, Bukit Batok is seen as a much safer seat.
Former MP David Ong, who stepped down over an alleged affair, won 73 per cent of the votes in a three-way contest.
The seat is also in the west, an area that has given strong mandates to PAP slates in the last few elections.
It also comes soon after GE2015, which saw the PAP gain a near-10 percentage point swing in votes.
Will these be enough for the PAP to avoid the potential challenges that lie ahead?
Deputy Prime Minister Tharman Shanmugaratnam acknowledged the opposition has a natural advantage in by-elections.
This by-election effect comes about when voters feel they can vote for an opposition candidate without worrying about voting the PAP out of power inadvertently.
In Hougang, the WP retained its seat but saw its vote share slip by 2.7 percentage points in 2012. In contrast, the PAP lost Punggol East in 2013 with a 10.8 percentage point erosion of its vote share.
This time round, there might be residual unhappiness over Mr Ong's sudden resignation just six months after voters had overwhelmingly backed him.
Mr Tharman said that in his rounds of the constituency over the past week, residents told him they liked Mr Ong as an MP but understood why he had to go and why the PAP acted swiftly once it found out about his issues.
But this does not address concerns that it is the second time in four years that voters are being put through the inconvenience of a by-election due to the personal indiscretions of a PAP MP.
Some who supported the PAP may feel the need to register their dissatisfaction at the ballot box.
National University of Singapore political scientist Hussin Mutalib said the PAP was hurt in Punggol East as a result of former Parliament Speaker Michael Palmer's affair. "The majority of Singaporeans by and large still do not condone such misdemeanours by politicians," he said.
Some also feel the PAP runs the risk of losing some votes by fielding a minority candidate.
The PAP has long argued that elections are not colour-blind, and GRCs are needed to ensure minority representation.
Mr Tharman recognised as much, saying that "race is never absent in politics anywhere", but added that the PAP was comfortable with its choice of Mr Murali Pillai.
That the party is putting faith in a minority candidate in a single seat amounts to a significant vote of confidence in Mr Murali's years of grassroots experience and his strengths as a candidate.
Up against him is Singapore Democratic Party (SDP) chief Chee Soon Juan, whose electoral impact cannot be discounted.
Singaporeans of an older generation might be wary of voting for Dr Chee given his past political conduct and brushes with the law, but he has sought to set aside his confrontational politics and cultivate a moderate image.
Dr Chee was a draw on the campaign trail last year, as supporters packed rally sites to hear him speak and formed long queues to buy his books and get his autograph.
PAP fields lawyer Murali Pillai for Bukit Batok by-election.
But his star power did not carry over to the voting booth, and his team got 33.4 per cent of votes in Holland-Bukit Timah GRC.
To stand a chance this time round, Dr Chee would have to engineer a very big swing - of at least 24 percentage points.
When the SDP contested Bukit Batok in GE1991 before the ward was drawn into a GRC, it got 48.2 per cent of the votes.But that was also the year when the SDP was at its peak and won three seats in Parliament.
The PAP has worked hard to win over 73 per cent of voters since.
But the road ahead will not be all easy and Mr Murali says he is bracing himself for a tough fight and no doubt knows a thing or two about close contests. His Aljunied GRC team almost pulled off an upset and scored 49 per cent of the votes against the WP incumbents last year.
Even before the by-election is called, Bukit Batok is shaping up to be a contest between two politicians who know what it is like to be the underdog.
A version of this article appeared in the print edition of The Straits Times on March 22, 2016, with the headline 'Quite a few unknown factors at play in Bukit Batok'. Print Edition | Subscribe
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