A referendum on changing the voting system was the biggest prize that Nick Clegg and the Liberal Democrats wrested from the Conservatives in return for their agreement to join the Coalition.
Had he not made this concession, David Cameron would have been forced to lead a minority government or – less likely, given the electoral arithmetic – to stand by as the Liberal Democrats went into coalition with Labour.
With the date for the referendum now formally set – 5 May next year – the question formulated – "Do you want the United Kingdom to adopt the 'alternative vote' system instead of the current 'first past the post' system for electing Members of Parliament to the House of Commons?" – and a minor Lords rebellion seen off, Mr Cameron has honoured his part of the bargain. The onus is now on the Liberal Democrats, as the most fervent supporters of reform, to pick up the baton.
Aside from the frisson that surrounded the House of Lords vote – the objection was linked to the fact that the Bill dealt not just with the referendum, but with reducing the number of MPs and equalising the size of constituencies – other hitches have cropped up. There have been fierce objections from some, especially in Scotland, that the vote will take place on the same day as devolved elections. And now the date of the royal wedding ensures a major distraction the week before. The Government has, rightly, stood firm.
The two sides are now forming their campaign teams, with the "No" supporters first out of the blocks. They boast five Labour veterans, including Margaret Beckett, who will be president of the campaign, David Blunkett and Lord Prescott, and two Conservative frontbenchers, the Foreign Secretary, William Hague, and the Justice Secretary, Ken Clarke. In a lighter footnote, the Education Secretary, Michael Gove, had his name taken off the list of prominent "No" campaigners after it was mistakenly added.
It is early days. But even now, the campaign has many of the ingredients, including heavyweight debaters and constitutional specialists on both sides, to make it a vintage political battle. Which is gratifying, because any change in the voting system is a serious matter and one that requires all the aspects to be fully aired. Best of all, the campaign will be that rare creature in British politics: an argument that crosses party lines.
While electoral reform has long been a signature issue for the Liberal Democrats, some of their number may object that AV is a pale reflection of the full proportional representation they sought. Most, but – as Mr Gove's pained intervention showed – not all, Conservatives oppose change, while the Labour Party is more evenly split. Mrs Beckett and Lord Prescott may be fronting the "No" campaign, but the new party leader, Ed Miliband, has said he will be voting "Yes". There is the hint of a generational divide here, which may become more evident as the campaign proceeds.
The Independent stands four-square behind reform. While we would have favoured more radical change, AV would be progress in the right direction. But convincing voters to forsake the status quo, however cautious the change might be, is never easy. The burden will be on the "Yes" campaign to make its case. It is time for the arguments to be heard.