I watched David Cunliffe face-off against Dr Brash on TVNZ Q&A. 

I thought Guyon summed up Mr Cunliffe's performance pretty well with the following quote:

"OK, David Cunliffe, this isn't a Labour Party speech."

Mr Cunliffe had the easy sell - playing on the emotion of keeping the assets state owned.  Yet he over egged it & sounded like a Party Political Broadcast - hence Guyon's comment. 

Dr Brash delivered a fairly solid performance. 

I think Mr Cunliffe would make a fairly good Labour Party leader if he managed to dial back his ego.  But based on David's performance on Q&A, John Key is as safe as houses.