Well obviously, but I guess they don't want to lose the few friends they still have. Its not like SWPers are going to get elected anyway.
I don't see how the SDP compares, as a flash party its a rather different thing.
It certainly didn't keep Thatcher in, giving 100% of the gains by the alliance from the '79 liberals to labour, which is ridiculous, still has labour losing, and around 40% prefered the tories anyway. Only in '92 was it close at all, and they did rubbish then anyway.
I mean really, don't Foot and Kinnock provide most of the explanation needed?