So now the real fight begins. If, as seems almost certain, we are to have a hung parliament, the UK's locked-down politics has suddenly been flung wide open. For the first time in living memory, we have a chance to smash our antediluvian system. If we can seize the opportunity a hung parliament offers, to deliver proportional representation and party-funding reform, we will change politics in the UK for ever.

Now we have the chance to be counted: metaphorically and literally. Our votes need never be wasted again.

But it won't happen by itself: nothing ever does. We will change this system despite most of the men and women who have just taken seats at Westminster, not because of them. Radical constitutional reform will happen only if we demand it, so loudly and so doggedly that parliament and government, whatever their composition might be, can no longer fend us off.

The fight starts tomorrow, with rallies in London, Glasgow, Manchester, Bristol, Middlesborough, Oxford and possibly other cities. It is being coordinated by the kind of wide-ranging coalition we've needed for years, as almost all the major reform campaigns – Power2010, Make Votes Count, Unlock Democracy, the Electoral Reform Society, Ekklesia, Compass, Hang 'em, Vote for a Change and others – have settled their differences and come together. (The only name missing from the list is 38 Degrees[see footnote], which appears to have decided that its real enemies are other democracy campaigns.) Most encouragingly, some of the big environment groups – Greenpeace, Friends of the Earth, the New Economics Foundation – have joined the coalition, knowing that much of what they hope to achieve is impossible under the corrupt old system. Greenpeace and FoE bring mass membership to the campaign, and their presence should encourage other NGOs to join.

So, now the UK has its own colour revolution. The colour is purple (my call for ginger sadly bit the dust). A few hours ago, at midnight, the coalition launched its site – www.takebackparliament.com – and this time, we're not expecting someone else to jump. In 1997, political reformers assumed they had got the result they wanted, and waited for the new government to reform our rotten system, as it had promised to do in opposition. And waited…

Now we aren't waiting any longer. Patience at times like these is no virtue. We'll beat down the doors of parliament until it gives us a fair, representative system, which is governed by the political choices of the whole nation, not just those of a few thousand swing voters in tight constituencies.

If you want your vote to count in future – in fact, if you care about any political outcomes – join up. It's the first chance we have had in generations. And it could be the last.

• More Guardian election comment from Cif at the polls

• This footnote was added on 7 May 2010: since publication of this article, 38 Degrees has contacted us to confirm that they are supporting this campaign.