HOW should a nice, middle-class chap commit political hara kiri?

Should he wield a Nigella Lawson pasta claw, a rolled copy of a Cambridge degree, or is a party political broadcast the best place for a belly-crawling mea culpa?

Nick Clegg, the Liberal Democrat leader and deputy prime minister, has chosen the third option, and the results will be there for all to see on television come Monday (it is already on the internet).

Mr Clegg is saying sorry for his U-turn on raising tuition fees. Before the 2010 UK General Election, Britain's answer to Mitt Romney was quite clear on whether or not the Liberal Democrats would back any rise. They would not.

But once LibDem posteriors were parked in the back of ministerial limos it was a different matter. From saying that they would vote against any increase, LibDem MPs duly trooped through the yes lobby at the Conservatives' bidding. Not all did so. Former party leaders Menzies Campbell and Charles Kennedy were among those who stuck to their principles. But 26 LibDem MPs followed their current leader, with the result that a "ker-ching" noise went up across the kingdom as universities rushed to charge the maximum for an education that many of those same capitulating Liberal Democrat MPs had once received for free. What bliss it was on that day to be a Scottish-domiciled or an EU student studying in Scotland. Everyone else: hard luck.

It was a catastrophic decision for students, for the party, north and south of the Border, and for Mr Clegg personally. Hell hath no fury like a voter scorned. It wasn't just students and their families who were scunnered. Anyone still holding on to the (albeit quaint) notion that politicians would try to keep their promises – ones they had shouted about from the rooftops, anyway – felt let down. Those lovely Liberal Democrats were not supposed to be like that. Yes, they fought like starving dugs over a bone when it came to by-elections, but they were really cuddly, principled sorts, weren't they? Reality then bit them, and us, on the backside.

If in any doubt about the state the LibDems are in, look at the numbers. In the 2011 Scottish Parliament elections, the number of LibDem MSPs fell from 16 to 5. That put them on the list with Scottish wildcats as an endangered species (and MSPs don't even have the saving grace of being cute). On the UK stage, a Populus poll shows support for the party running at 10%. Dissatisfaction with Mr Clegg is up from 58% to 66%. Bar former Rangers owner Craig Whyte standing for election in Govan in 2015, could there be any politician more on a hiding to nothing than Mr Clegg?

Mr Clegg is now expected to face mass grumbling at his party's annual conference, which starts in Brighton tomorrow. Stand up and be counted or stand down is the gist of the gurning in some quarters. It is usually the Tories who, after the regicide of Mrs Thatcher, are characterised as the nasty party when it comes to dispatching leaders. The LibDems, however, are hardly amateurs. Look how they treated messrs Kennedy and Campbell. If the rank and file believe dumping Mr Clegg will save their skins he has as much chance of survival as a chicken gatecrashing the annual conference of the Fox Party.

Hence the apology. The mea culpa. The je regrette something-or-other statement. "There is no easy way to say this," he says in the broadcast. "We made a pledge, we didn't stick to it, and for that I am sorry."

Note that it wasn't the policy that was a mistake – it was promising to vote against a rise under any circumstances that was the error. It is still apparently okay to saddle youngsters with decades of debt, but he shouldn't have pledged that he would not. Dance on that pinhead of logic if you will. No wonder that by last night internet wags were falling over each other in the rush to spoof the PPB. One video is to be sold on iTunes.

Contrast Mr Clegg's quasi-apology with his insistence, two years ago, that he was not going to apologise "for one minute" for his U-turn. He got that right. The apology to be aired on Monday takes two minutes and 39 seconds.

It takes a special talent to stuff-up an apology for your original stuff-up, but Mr Clegg has managed it. This is not so much witnessing a double U-turn as watching a political career go down the U-bend.

Vince Cable, the Business Secretary, and David Laws, the Education Minister, joined in the apologies yesterday, with Mr Cable calling the original pledge an "unwise commitment". Clegg, Cable, Laws: eight more and they can call themselves Whoops United. What can be behind such a gamble, and will it work?

Answers, in obvious order, are "sheer lunacy" and "no". The reputation of the LibDems has sunk so low not just because of the tuition fees U-turn. It is a huge factor, but it is far from the only one. What sticks in the collective craw of voters is not just one mistake, but standing by the Tories as they have made blunder after blunder, chief among which is carrying on with a programme of indiscriminate cuts while growth flatlines. And when it came time for payback, to claim a prize for all that kowtowing to the Tories, they opted for, of all things, voting reform – only to mess that up as well.

This is nothing personal against Mr Clegg. It is strictly political, because as a political animal he has shown himself time and again to have as much nous as that Nigella Lawson pasta claw.

The only factor in favour of the mea culpa strategy is that things cannot get much worse for Mr Clegg. He cannot move on without apologising, so he had better get on and do it as far away from the next UK election as possible. What a mess, to have gone from large numbers of voters saying "I agree with Nick" during the election debates, to Nicky No Mates.

Some good will come out of it. In years to come, some lucky student, fresh from a night shift stacking supermarket shelves, will sit down to a politics exam. On the paper will be a question a five-year-old could answer, to wit: "In recent history, who did most to turn the Liberal Democrats into a dodo?" The answer will be squawking in Brighton next week.