Sunder's thoughts on possible future Labour-Lib Dem coalitions prompts me to offer some not entirely tongue-in-cheek thoughts about another, long-term possibility: merger.
Of course, there are party tribalists in both parties who oppose this and they will make sure that it probably never happens. But as someone who has spent time in both parties, without any substantive change of views, I think its worth at least setting out the case for why a merger might, in the long-run, make a kind of sense.
Basically, it is hard to see what the big philosophical difference between Labour and the Lib Dems is. State socialism - a planned economy based on direct state control of economic activity - is, thankfully, no longer a Labour aspiration. Like the Liberals of old, Labour wishes to advance egalitarian objectives within the framework of a regulated market economy. Indeed, in some areas, such as 'asset-based welfare', Labour now does a much better job of advancing radical liberal economic ideas than the Lib Dems do.
On the other hand, notwithstanding the recent efforts of Clegg and co. to reposition the Lib Dems to the right on tax policy, the Lib Dems remain essentially a party of the centre-left on the economy. In short, both parties share a progressive vision on the economy which includes markets, an active state, and efforts to spread and democratise property ownership.
One might argue that there is a difference on civil liberties, and I think there is a difference in party cultures here (one which entirely favours the Lib Dems). But this difference can be overstated: the Labour government's often draconion stance on civil liberties is one that worries many Labour party members as much as it does Lib Dem members.
And, to the extent that there are differences in culture between the two parties, it is possible that merger could draw constructively on these differences. The greater Lib Dem sensitivity to civil liberties might infuse the merged party. At the same time, Labour's political culture could help infuse a merged party with a greater sensitivity to issues of class than the Lib Dems sometimes show.
So: why not merger?