There is a small but significant difference. Without the SDP joining, the WP has a small but significant chance of winning. With the SDP joining, that chance is basically zero.
SGParent asked me a question he thinks has an obvious answer: are SDP's antics good for the opposition cause? Suppose SDP contests. They they get raped and lose their deposit. Then they have to fold because they have no credibility, and 2016 takes place with SDP no longer being a credible force. Good or bad?
Or in a 3 corner fight, what if WP and SDP both get 25%. Then we have 2 strong opposition parties for 2016. Good or bad?
You can say that when WP and SDP are not fighting for a seat anymore, this by-election is not important to them. I say think about it this way: This by-election has turned into a report card. This report card could be ultimately more important than one seat.
Honestly speaking, we need as many opposition members in parliament as possible. What is important is not how loud the voice is but how many would-be voices are there.
How really loud are these PAP voices in parliament? Not very loud. In fact a fair number are missing most of the time. And even if they are there, they could be silent. Compared to them, WP MPs are relatively vocal. Each usually has some questions to ask according to the specialization assigned to him. LTK seldom speaks nowadays because I believe he was assigned nothing. I guess if it is a question regarding his party he will speak up.
But when it comes to something that needs a vote, all these PAP voices will come across loud and clear and no opposition can block that decision. Unless that number exceeds one-third, then they can block some decisions but only the game changing ones. Today they are totally at the PAP's mercy.
The PAP can change things equivalent to not having to have any election. Although it might appear incredible, the power of the PM to decide whether to have a BE is very good example. You don't think it is possible for them to do away with General Elections every five years altogether? How about no need for GE if there is no referendum asking for it? Still democratic. Right? Except that it is very difficult to demonstrate it. Why are they not doing it? Because they fear the people. Even the 60.1% dafts, with the possible exception of our entertaining bro (or sis) Kinana, will object to this.
But today, they have the power to merge an SMC with a GRC without feeling great remorse because they know any misgiving of the voters will dissipate in the next five years and be totally forgotten. So don't say a single seat lost to the PAP for the opposition is nothing. It could be a single seat lost forever.
If SDP does not harm another party's seat while gaining its own, then they should be in parliament. But on the other hand, if they are just playing zero sum games, taking over somebody else's seats, then I rather they be replaced by a new party that can advance the Opposition cause of gaining one-third representation in parliament in the shortest time and eventually to a simple majority.
I don't think any party, opposition or the PAP should aim for more than two-third majority. Not only is it too greedy, it is not ethical as this clause is there to protect the rights of the minority. In a commercial contract, the equivalent clause is what is called the super-minority clause where the minority has a veto right.
I also want to challenge the PAP's concept of the parliament being a two sided debate: the ruling party versus the opposition. It should be a place where the best ideas should come from the whole parliamentary body itself especially when the majority margin gets closer to zero. You cannot just ignore the wishes of that large number of people. If such a parliamentary working were there in the first place, we would not have got into so many policy mishaps in recent years.