He needs to be careful that Brown doesn't call his bluff.

Which is more important to him - PR or getting Brown out ...

... and more importantly - which is more important to Liberal voters ...

They will feel betrayed if he doesn't accept Browns offer of an immediate referendum.

The Next Government will be short lived whatever happens - best to make sure that when the next electon is called, that it is a fair one.

If it's called in 3 days it will be First Past the Post and they will lose this wonderful opportunity to force through electoral reform.

I can't see how the liberals have any other choice.