A slightly unusual thing happened at Deputy Prime Minister's questions today. Nick Clegg had a go at the Tories. This in itself is not as unusual as many readers of The Staggers might think (nor as common as many Lib Dems would like) but what was remarkable was the target. Not a ragtag of Tory backbenchers (though the ever-reliable Peter Bone teed it up for him beautifully), but the Conservative chairman, Grant Shapps. In response to rumours that the Tories think the Lib Dems will do a "cash-for-boundaries" deal, Nick quipped:

I've already read in the press, reports that the chairman of the Conservative Party wishes to strike a deal with us on boundaries in return for a party funding deal. I suppose, Mr Speaker, finally that’s a get rich quick scheme that he’s proud to put his name to!

So, why does Nick suddenly feel able not only to say a confident "no" to proposed Tory policy, like welfare cuts, but also to start openly mocking his cabinet colleagues?

Well, partly it must be irresistible at the moment. Given the list of Conservatives in the cabinet whose position has appeared untenable at various points in the last few months – Jeremy Hunt, Andrew Mitchell, Shapps, and now Justine Greening – it must be like shooting fish in a barrel. And, partly, we are now more than halfway through the current Parliament, and the Richard Reeves positioning strategy moves from Phase A to Phase B (just 30 months too late, but, still, we’re there now).

But it's also because the Tories probably know that the received wisdom that a collapse in the Lib Dem vote benefits them is wrong. As this excellent analysis shows, such an outcome is far more likely to benefit Labour. So, bizarrely, the Tories probably need to allow the Lib Dems to do a little better in the polls if they are to stand any chance of winning a majority at the next election. Therefore, they have to take some poking from their coalition partners with a certain stoicism. It’s a short term loss for a long-term gain.

It also puts Labour in a tight spot strategically – spend the next two years bashing the Lib Dems and there’s far more chance of an electoral reward at the ballot box. But should, having made a lot of enemies in the Lib Dem camp, they fail to get over the line – what then?

For now, the Tories know that, in the absence of the boundary changes, their best hope for electoral success lies in a revival in Lib Dem fortunes. They’re going to have to take a lot more Grant Shapps jokes from their coalition partners in the coming months.

Richard Morris blogs at A View From Ham Common, which was named Best New Blog at the 2011 Liberal Democrat Conference.