David Cameron was elected to lead the Conservative Party for his political and presentational skills, not his convictions. It remains to be seen if he has any convictions, but now we must also question his skills.
He has a tendency to give hostages to political fortune. He tried to seize the moral high ground on becoming party leader by pledging to avoid "Punch and Judy politics". He has been persistently prodded with political pitchforks by Mandelson and the lesser demons ever since, but if he responds in kind, they jeer "Punch and Judy" at him. I fear the phrase "cast-iron guarantee" is going to haunt him in a similar fashion.
People don't trust politicians and it's not entirely their fault. It is a defect in democracy itself that if you don't tell people some approximation of what they want to hear, you can't get elected. We all like to believe in the wisdom of crowds, but the truth is that the majority of modern Britons want to hear that the state will solve life's problems, without effort or cost to them. Politicians are torn between over-promising to stay in power and the fear of their lies becoming so obvious as to discredit them. Their corruption is a mirror held up to decadent, economically-ignorant, essentially amoral voters.
Politicians' careers are an assault course, during which they sustain repeated political injuries. For a while they run on bravely, but eventually the damage is too much and they fall. The most typical injuries are failures to deliver on those promises they would have preferred not to give. Gradually, inevitably, they become too discredited to continue.
Margaret Thatcher was the exception. She was principled. She promised nothing she could not deliver and she was utterly relentless in making sure she did. In pursuit of her objectives she fired one minister after another, making enemies within her party faster than outside it. In the end, the pygmies with wounded pride were numerous enough to bring down a political giant. I was at a dinner in the City with Francis Pym, prominent among the pygmies, on the night she fell. As all my hopes for the arrest of Britain's decline died - I bitterly watched him drink in gleeful celebration. There must have been dozens of others doing the same that night.
But Cameron's injuries were never going to be of Thatcher's kind. He is one of the pygmies, lacking her political courage and her moral vision. His was always going to be the routine political failure of one too many broken promises. That's why his "cast-iron" pledge of a referendum over Lisbon was so foolish. He will now suffer more injury from every future broken promise because of one broken before he even took office. A promise he need not have made.
A referendum only made sense if it would prevent the adoption of the EU's constitution-in-all-but-name. Once it had been adopted, any referendum (as the Euro-sceptics baying for it well know) would be on our continued membership. The issue of the EU dangerously divides the Conservative Party. Any Conservative leader must manage the issue constantly and cleverly. Cameron's mistake was not to break the promise. It was to make it in the first place, and to make it - again - in such memorable terms.
Margaret Thatcher will go down in history as the Iron Lady. This farce means that Cameron will be remembered, if at all, as "Cast Iron Dave".