I wonder if Nick Clegg is not beginning to over-reach himself in stepping up the kind of demands he would make in support of either a Tory or Labour Prime Minister.

It is of course in his interests to keep the focus as much on process as on policy, because it is the former that gave him his remarkable post TV Debate 1 boost; but the latter that is responsible for the apparent peaking (usually in my experience followed by a fall unless it comes right on voting day) of support.

It is difficult for him to avoid the process questions when, with the polls as they are, they point to his pivotal position within a possible hung Parliament. But what he has done in the past 24 hours is signal that far from being the more attractive alternative to David Cameron, he is now openly ruminating on the possibility of being the other side of the Cameron coin, whilst being far more agressive about the possibilities of working with Labour under Gordon Brown.

The Lib Dem activists I know are unlikely to be that keen on a Cameron-Clegg government. The Tories I know are unlikely to welcome the commitment to electoral reform Cameron would have to give, which would effectively mean John Major was the last Tory leader to get an overall majority. And members of the public I know who are flirting with Clegg are doing so in part because he did well in the first debate, but also because they see it as a cost-free way of getting change without getting Cameron.

But that is the problem. What you end up with is Cameron. And the reason the Tories are not home and dry already, despite such favourable weather for them, is that the country does not seem to want Cameron.

Meanwhile, in a piece of spinology worthy of the best, the Tories have managed to persuade the more gullible among the media that they are now able to extend their list of Labour target seats.

What their briefing actually indicates is that despite all the focus on Clegg, the real battle remains in Labour-Tory marginals, and the ‘vote Clegg, get Cameron’ approach is the one likeliest to work best for Labour in those seats.

It is partly, I admit, wishful thinking, but also my experience of observing David Cameron over the past four years, and Mr Clegg over the past few weeks, that leads me to believe Cameron is still struggling to break through with the voters he needs for an overall majority, and that the Clegg bubble may well burst in the next few days.

What matters then is where the air from that bubble goes, whether it falls left, right, up, down or to none of the above. One thing is for sure – the Tories’ belief that it will all go their way, if Labour’s weekend canvas returns are anything to go by, is mistaken.

This election has had many twists and turns already, of which Mr Clegg’s rise has been the most dramatic. But there are plenty more to come.

** GB at the Royal College of Nursing at the moment. Storming it. Showing that when it comes to substance and policy, he beats the other two every time. Clegg/Cameron for PR, GB for PM. Powering through on substance. All to play for as economy moves even more centre stage.

*** Buy The Blair Years online and raise cash for Labour http://www.alastaircampbell.org/bookshop.php.