The popularity of a certain party might rise or fall not because of itself, but for the fall or rise of the opposite party. The Democratic party won the majority of midterm election in 2006 not because of itself, but because the people was wary of and just couldn’t stand the second Bush and the Republican party. It was actually a vote against the Republican. Could we, then, have some kind of negative vote system, where you can actually vote against a certain party without voting for another party? Admittedly, negative vote is not constructive, since basically you could only say “no” without indicating what kind of “yes” you want to be. You could only identify the problem but not the solution. And most of the times perhaps life is just like that. You know something is wrong with the PAP, but you couldn’t say that SDP or WP would be better either. And I guess that’s why most of the times as well we are willing to vote for the other party to express our actual vote against a certain party (and usually the ruling one). We are willing to take the risk of trying something new — before we found ourselves to be disappointed again with the new establishment.
On the other hand, ironically somehow the opposition likes to paint themselves as the opposite (duh!) of the ruling party as well, without actually delineating what their identity is positively. Their identity is based on the ruling party. We are the “Not-government.” Certainly this kind of approach could be proven popular and ride the emotional anti-establishment wave of the people in the short term, at least until the election. But when the “Not-government” wins, sadly sometimes the “Not-government” doesn’t know how to govern as well, and could be even worse than the previous ruling party.