As I said at the time of the Punggol East by-election, the SDP chickened out. It is as simple as that. In fact a counting agent of the SDP's during GE2011, and one of its staunchest supporters, said as much, although he does not use my stark description:
'Even though the SDP’s statement to the media was that they “decided to withdraw from the race” because “Singaporeans have signaled clearly that they do not want to see a three-cornered contest in Punggol East which may dilute the vote and allow a PAP win,” adding that “We hear their voices and we have heeded them,” everybody can see that they must have taken a sober look at their chances and seen the prospect of humiliation staring back at them.'
That is Alex Au's view. Not necessary that I have to agree with it.
SDP should know that they are against multi-cornered fights. They also want the last contesting opposition party to have priority over the same ward and I'm sure they will not want WP or NSP to contest Sembawang GRC or Bukit Panjang in 2016.
As what some observers pointed out back then, SDP announce they contest PE then withdraw in the name of unity hoping that WP will reciprocate in 2016.
This appears naive but at least it is not damaging.
But along the way, of all people, its own emotional leader deviated from the message and added power-sharing schemes, releasing emails and other bizarre antics. He thought by doing that will show they are serious, but people ended up seeing them as desperate, power-hungry and rude.