Punggol East, 4 corner or 2 corner fight?

It is now confirmed that four candidates have submitted their nomination papers and accepted for the by election. Koh Poh Koon(PAP), Lee Li Lian(WP), Kenneth Jeyaretnam(RP), and Desmond Lim(SDA) will be standing for their respective party. Somehow I still look at this as a straight fight between PAP and WP. As for the other two, very likely both will lose their deposits, $16k!
This looks set for