TFBH
How do you see things playing out in Punggol East? Going by your analysis, RP and SDA are in the position as TKL vs TJS. Just. As TKL was unable to position himself in a meaningful way, it is hard to see how SDA and RP can position themselves in a way that disinguishes them significantly from WP. Unless they unviel something shockingly bold, they are going to suffer the same fate as TKL.
I agree that there will always be a small minority that chose because of demographics like gender, race and other reasons. From GE 2011, their number in Punggol East is about 1,3000. I am projecting their numbers to fall this time to under 1,000 which will be shared between RP and SDA. Unless I see good turnouts at their respective rallies, I am going to stick with this number.
Incidentally the law against publishing election survey results is because of the impact such results can have on actual results. It has been empirically proven that survey results which show candidates gaining strength or momentum can often lead to more people wanting to vote for the person. The best recent example of this is from the recent elections in the US where Romey surged after a whole series of opinion polls showed that he had beaten Obama in their first debate. The most common explaination for this is that people like to vote for winners because they do no like to admit they voted for a loser.