Nice try Alex.
If Cameron had agreed it would play into Salmond's agenda that Scotland is being held prisoner by England.
Cameron is quite right to say that Alistair Darling is the right man to debate with Salmond.
Salmond doesn't want that because he wants to push the 'no true Scot' strawman.
In his view 'no true Scot' is opposed to independence.
But this is also an attempt to turn attention away from the run of bad news he's been getting.
It's bad enough that Scots are fed up with his obsession about independence.
It also seems that his hope of rigging the vote by bringing in 16 & 17 year olds may not work after 75% of schoolchildren voted against independence in a mock poll.
Finally, a couple of weeks ago, I read a piece that made a lot of sense. It's point was that there was a big difference between the notion of Scottish independence and the possibility of independence under a socialist dictator. Its key point was that Salmond was the wrong person to trust with independence and I wanted to link to it but when I searched for 'Alex Salmond' 'wrong' I got too many results to be able to find it.