I have signed in my personal capacity a letter organised by Richard Reeve of Demos in today's Guardian. It says a great opportunity for reform is opened up by support for the Liberal Democrats and calls on Labour and Tory supporters of democracy and liberty to switch to them.

This is an extraordinary political moment. An election seemingly destined to produce a narrow Conservative victory has been seized by the voters and turned into a democratic contest – a contest not just between parties, but over the shape of our democracy itself.

What offers the best chance of democratic reform?

The question is where the energy for the future of progressive politics is to be found. It is a contemporary political fact that the stronger the performance of the Liberal Democrats on 6 May the better the chances of progressive reform.... Long-standing party loyalties, even in a less tribal world, are not easily suspended. But May 2010 offers a once-in-a-generation opportunity to reshape politics for the better. It must be seized.

When I signed I said I'd blog to add that by Liberal Democrats I mean them or other smaller parties or independents where they have a chance of winning, such as Caroline Lucas in Brighton Pavilion and the SNP in Scotland and Plaid in Wales. "I am for pluralism led by the Lib Dems not the Lib Dems monopolising pluralism!" This is the Hang 'em strategy now signalled by George Monbiot in his excellent call for post-election unity of those who want change in Britain needs a Ginger Revolution and Rory Cellan-Jones at the BBC. It is not the same as the strategy in the letter, which is closer to David Marquand's, but the main thrust is. The critical point is this: we must stop either the two main parties from getting their monopolistic hands on the hyper-centralised UK state.