We can certainly be clear about one thing; whatever inspired David Cameron's comments to me on the TV debates this afternoon, it was not a new found love of the Green Party.
The Tories just basically want to avoid the TV debates, or at least any version of them that resembles what happened last time. There a number of reasons for this:
1) They have a big war chest and the support of the vast majority of the press (even the Guardian seems curiously cool on the prospect of a Miliband premiership and Ed can really only rely on the Mirror for steady support). In addition, most commentators at Westminster think the Tories will probably scrape home one way or another. All these things give them a huge inbuilt advantage that can only be undermined by allowing any opponents more air time.
2) David Cameron's advisers think he would do well in the debates - after all he was considered to have won the third and possibly even the second last time - but they also concede that Ed Miliband is nowhere near as ineffective as they like to claim. Given that public opinion of Ed is pretty low and he is clearly an intelligent man, he can arguably only improve his ratings.
3) They do think the debates dominated the campaign in a slightly unhealthy way last time.
4) They think (and they're right) that the basic law of TV is that it has an inbuilt bias in favour of anyone who appears fresh and new. Nick Clegg did well in the first debate last time around, but part of his appeal lay simply in the fact that he was a fresh voice. This is mostly likely to benefit Nigel Farage this time, which is another headache David Cameron feels he doesn't need.
5)They argue that including UKIP, which primarily poses a threat to them, and not the Greens, who represent a challenge to Labour and the Lib Dems, is simply unfair.
So what happens next?
We are in the middle of a complicated chess game and there are quite a few potential outcomes:
1) The broadcasters decide to allow in the Greens. This would almost certainly force the PM to take part and might even allow them to go ahead on the timescale the broadcasters want (David Cameron has argued all of the debates should happen before the campaign starts). But this could leave the broadcasters with a massive headache. If Ofcom has suggested the Greens deserve major party status, what is the logic in including them and not the SNP, who could, on current projections have more than twenty MPs and perhaps hold the balance of power? Of course, the Tories know all this, which is why the love in with the Greens looks like their get out of jail card.
2) David Cameron decides to do them anyway because it is the 'right' thing to do. One very old and close ally of his told me a few months ago; 'the trouble with David is that he can be terribly fair-minded.' It was said in nervousness and perhaps even frustration. For the moment, it looks as if political David will win out, but it is not inconceivable that this might change.
3) The Tories, who are thoroughly p***** off with the broadcasters, agree to an alternative proposal - probably the Youtube/newspaper one - and say they are prepared to debate all parties with MPs in the Commons as long as it is before the campaign starts. If they wanted to be really mischievous, they could argue that the BBC, as the leading public service broadcaster, should carry these debates in prime time (without having any control over them).
4) They could pick a neutral body to host a debate involving leaders of all parties with MPs in the Commons and suggest all broadcasters might want to carry it live (in the full knowledge few of them will).
I currently rate option three or perhaps four as marginally the most likely.
The Tories probably do need to be seen to be willing to debate all comers. They can make a virtue of saying they are reaching out to the Youtube generation and trying to do things differently.
And, of course, involving lots of leaders will guarantee the event is cumbersome, verbose and lacking in any kind of drama.
This will suit the Tories just fine, because it will also ensure it has no impact whatsoever on the floating voters whose interest in politics is limited and who might watch a prime time debate on the BBC, ITV or Sky but are highly unlikely to watch this.