No one should doubt David Cameron's commitment to the Union but there's at least one reason why Scottish independence wouldn't be an entirely negative outcome for the Tories. The break-up of the Union and the removal of Scottish MPs for Westminster would dramatically reduce the chances of Labour returning to government. It's well known that Ed Miliband has more Scottish MPs than Cameron but what's less well known is just how many more. Labour won 41 seats at the last election (no change from 2005) but the Conservatives won just one (see graph). Indeed, the Tories haven't exceeded that figure since 1997. There are now more giant pandas in Scotland than Conservative MPs.
As a result, the commitment of some Tories to the Union has waned. In 2006, Michael Portillo told Andrew Neil: "From the point of political advantage, the Conservatives have a better chance of being in government if Scotland is not part of the affair. You are continuing to assume the Union is sacrosanct. That is not an assumption I make any more." A 2009 ConservativeHome poll of 144 party candidates found that 46 per cent would not be "uncomfortable about Scotland becoming independent". To many Tories, an independent England - economically liberal, fiscally conservative, Eurosceptic, Atlanticist - is an attractive prospect.
On his live blog, the Guardian's Andrew Sparrow reports on speculation at Westminster that George Osborne, who is chair of the ministerial group on Scotland, is "not the union's greatest fan." It's not hard to see why Osborne, who is also the Tories' chief election strategist, might be tempted by the prospect of an independent Scotland but, to date, there is no evidence that he's anything other than an Unionist. However, you only need to look at the graph above to see why some in the Conservative Party are not.