Four weeks ago, with predictions that turnout in the election then about to be announced would hit a historic low,
The Independent on Sunday launched its One of the Above campaign. The aim was two-fold: to persuade those hundreds of thousands of eligible voters who had failed to register to do so, and to suggest that, in spite of any understandable misgivings about politicians, as many of us as possible should use our vote.

In the first of those aims, hundreds of thousands did register, particularly the young; and on the second, turnout looks likely to climb out of the valley of apathy of the last two elections, buoyed by a close race and perhaps by the television debates. So far, so good.

Now though, as polling day approaches, for the logical extension. The underlying principle of the One of the Above campaign is to make sure that the democratic will of everybody is expressed equally, and that, we believe, is impossible under the discredited first-past-the-post system. Never again should the vast majority of votes be deprived of any impact on the outcome.

So today we begin our campaign for a fairer system with a plea: in this election of all elections, the opinion polls, in signalling a hung parliament, suggest a historic opportunity for change that, as Nick Clegg suggests to us today, may not recur for a generation. And that compels us to suggest that readers should consider voting tactically on Thursday.

What do we mean by that? As the Tories are opposed to electoral reform and are ahead in the polls, we are asking voters in 85 key constituencies to vote for the candidate best placed to frustrate David Cameron. This is all the more urgent as our ComRes poll today suggests that he is poised on the very edge of securing a majority. We publish our guide to the mechanics on page 19.

This is not because we dislike Mr Cameron. We may still be unsure whether he stands for the environmental approach that he emphasises to us today, or for the unlovely politics of immigration he trumpeted in the television debate on Thursday. But the reason for opposing him is that this self-professed candidate of change refuses to consider the most vital change of all. From electoral reform flows much else that we believe this country needs: green jobs, a fairer tax system, an urgent defence review and sustained investment in health and education.

These values are perhaps best espoused by the Liberal Democrats, and one of the pleasing features of this campaign has been the realisation at large that Nick Clegg is a formidable politician, leading a strong team.

Why, then, do we not make it simpler and say: vote Lib Dem? For two reasons. First, one of the anomalies of the present system is that voting Lib Dem could hand scores of Conservative-Labour marginals to Mr Cameron - as Peter Mandelson correctly points out on page 41. Secondly, we do not believe that to reduce the Labour Party's share of the vote to a historic low would be right. Indeed, the best outcome of this election would be a Lib-Lab coalition.

This newspaper has long defended Gordon Brown but is not unaware of his failings. He is a radio politician in a television age, and that has cost him dear. He has been around a long time, and that has had its impact in an era when the mantra is for change. And he has not succeeded in persuading voters that his personality defects are irrelevant to the question of effective government. Yet there is a magnificence about Brown and, on the rare occasions when this election campaign has addressed matters of substance, most importantly the economy and the deficit, it is a case of "no time for novices". And Labour has done an impressive job in 13 years, whatever the failings, notably of foreign policy.

We debated whether it was right for us to dare to advise our readers. But we think we should be clear. We worried that to ask for an anti-Tory vote in selected constituencies might seem negative. But we are convinced that nothing could be more positive than to secure a change to a fairer voting system. No one should be scared of a hung parliament: it is the key to progress.

We called on Britain to register, and we call on you to vote. If you are convinced by the Tories, then please give Mr Cameron your considered support. But if you believe that we are on the cusp of a once-in-a-lifetime opportunity, then join with us, and vote for the change that really matters. Use your democratic right to enhance the democratic rights of all. Vote for a hung parliament, and a better, fairer, greener Britain may just be ours.