Let's play a game of fantasy headlines – or rather nightmare headlines. What would each party leader least like to see splashed across tomorrow's front pages? Here's a guess: "Tory war erupts over Europe", "Lib Dems break promises" and "Labour bottles out of opposition". Yet any of those three could be written about today's vote on a European referendum. And it's extraordinary that each party leader has allowed it to happen.
The Lib Dems have been in favour of an in/out referendum on EU membership for years. They first backed it out of cynicism, as a way of avoiding having to vote for a referendum on the Lisbon Treaty in 2008. Here's what Nick Clegg said at the time: "Nobody in this country under the age of 51 has ever been asked that simple question. That includes half of all MPs. We've been signed up to Europe by default: two generations who have never had their say."
Well, today Lib Dem MPs at last have a chance to vote to put that right. Parliament is debating the call from 100,000 voters for a referendum on EU membership. But instead the party has issued a three-line whip to force its MPs to vote against. If Clegg speaks in today's debate, he will doubtless cite his slightly more nuanced 2010 manifesto, which calls for an in/out referendum only in the event of Britain signing up for "fundamental change in the relationship between the UK and the EU".
But the reason why there is even talk about a referendum now is because there is an imminent prospect of fundamental change in the EU. The eurozone countries are contemplating much greater political and economic union. All 27 member states will have to agree to that, which will give us the chance to demand changes in return.
Unlike the Lib Dems, Labour has never been in favour of an in/out referendum, so the party isn't open to the same charge of hypocrisy. But it still seems odd for Labour to line itself up so firmly with the Government, which it is supposed to oppose, and against the people, two-thirds of whom said in a YouGov poll yesterday that they wanted a referendum. Ed Miliband has been telling his MPs that he opposes one because he doesn't want to look anti-EU. But offering the public a say is quite different from backing a "no" vote – as Clegg could have told him until recently.
The leader with by far the most to lose, though, is David Cameron. And I find it almost inexplicable that he has deliberately set himself up to face the largest rebellion ever suffered by a Conservative Prime Minister over Europe – even bigger than John Major endured during the dog days of Maastricht in the 1990s.
Cameron should be worried that his MPs were recalling those dreadful times yesterday. "It's very reminiscent of the Major days: all this petulant machismo," said one former minister who served in that administration. But the difference is that Major believed he had to get his Maastricht ratification Bill through Parliament. Cameron is under no such pressure.
Today's vote is a backbench business motion, which is up for debate because voters signed a petition. It is not a government Bill. The result isn't binding. You could argue that it's not even appropriate for party leaders to impose a whip on debates arising from petitions – it's tantamount to sticking two fingers up to the public. Parliament should instead have an open debate and a free vote. It would then be up to the Government to decide whether or not to act on the result.
If there had been a free vote, the motion might not even have been carried. But if it had, Cameron could easily have said, "I hear what you say. I agree that any renegotiated relationship with the EU will have to be endorsed by a referendum. But it's too early to call one now, when we don't yet know what shape the eurozone will take or what any new relationship will look like." He would have sounded both responsive and responsible.
Instead he has absolutely infuriated his party. Iain Duncan Smith, the Work and Pensions Secretary and former leader, has been grumbling to rebels in the Commons tea room, making no effort not to be overheard. Owen Paterson, the Northern Ireland Secretary, has refused to rebuke his PPS, Stewart Jackson, who is planning to rebel today. And that's just the Cabinet ministers. Further down the food chain, there is a huge amount of anger and distress.
MPs who are on record saying that they would back a referendum will either have to do so and lose their jobs and any chance of promotion or explain to their constituents why they have broken their promise. Their only excuse will be that the whips bullied them into it. What will that do for the contempt in which politicians are already held?
The Tories are supposed to be in favour of giving more power to the people. Instead they are showing disdain. They are bulldozing parliamentarians to vote against a people-led petition. And in the process they are depriving the people of the chance to have their say on Europe. Voters already believe that, over the past few decades, politicians have misled them about the EU and made huge changes to the relationship without consulting them. Many of them, though, thought that Cameron and William Hague would be different.
Both the Prime Minister and the Foreign Secretary know that great opportunities lie ahead for Eurosceptics. If there is going to be a new treaty, which there must be if the Eurozone is heading for closer union, then Britain and other non-euro member states will have the power to insist on changes that suit them. Cameron and Hague will be saying so in their speeches to the Commons today. But what better way of improving their negotiating position in Brussels than to cite the need to win a referendum at home?
The European Commission is terrified of referendums. It has seen its plans founder so many times at the hands of recalcitrant national voters. And the British are probably the most recalcitrant of all. The threat of a referendum could help the UK win all sorts of concessions.
So if Cameron had allowed a free vote today, he would have given the right of his party a chance to let off steam harmlessly. He would have strengthened his hand in EU negotiations while still retaining control of the timing and subject of any referendum. He would have looked as if he were listening to the people rather than slapping them down.
Instead he has fuelled hatred and anger in his own ranks, disillusionment among the voters and a public perception that the Tories are back to their old tricks, splitting over Europe. What a bizarrely self-inflicted wound!