SDP's (or rather Chee's) idea of a joint candidate was so flawed on so many regards. It was not, definitely not, akin the coalitions partiesin other countries as much as his posts on the SDP website said so. So now you have a sort of weak argument from Low. SDP's try was useless in the first place. Low isn't the best debater to argue but his argument stands better than SDP's/Chee's logic then.