Oh dear. Nick Clegg has had another Shylock moment, bewailing his lot to the New Statesman. Has a Lib Dem not hands, organs, dimensions, senses, affections, passions? "If you prick us," he wails, "do we not bleed? If you tickle us, do we not laugh? If you poison us, do we not die?"

The short answer is no, not if you are a minority leader in a coalition. Then you are lower than a cur. You are a fence-sitter, a turncoat, a scapegoat, a liar, a pledge-breaker, a class traitor, probably a scumbag into the bargain. You are a stock-in-trade figure of fun and/or hate. Little old ladies quake at your name. When children won't go to bed and are threatened with a "right Clegging", they scream in terror.

His latest howl of pain breaks the number one rule of being on top: never show it hurts. Never say, as he did: "I'm a human being, I'm not a punchbag." You are not a human, you are a government minister. You lie for your country and are therefore a punchbag. Above all, never mention the children's question: "Daddy, why does everyone hate you?" It suggests that everyone does hate you, that the playground mafia is on message, and that you probably should have stuck to market gardening.

Watching the hormonal onset of Clegg's political puberty has been difficult for us all, but it was easy to predict. When he rose to television stardom a year ago, it was clear that the ecstasy of impending power could only lead to agony. Lauded as a Churchill, an Obama, a weather-changer and kingmaker, he pledged "an end to the same old broken promises". He should have known that coalitions always break promises. They involve an hour of freedom and a lifetime's servitude.

Thus it has turned out. Clegg was always going to be a blind date and a one-night stand, David Cameron's coalition arm-candy. He looks and sounds miserable and alone. Cameron even makes him go by train standard class, which is outrageous. To the New Statesman he was "so tired he appeared taxidermied". Such exposure should never have been allowed by his staff.

Last May Clegg decided to play advanced level extreme politics. It would be tough even for a man of great experience in power – and he had none. Liberals had not exercised collective government responsibility since before women won the vote. It had been a gadfly party, a ginger group, a dustbin vote, free to make pledges on student fees, greenery and taxation that no one expected it to have to honour. The Liberal Democrats were nearer to a student debating hall than a corridor of power.

The coalition marriage ceremonies were performed by Clegg with aplomb. He rightly judged that Cameron's Tories briefly needed him more than he needed them, and he extracted top jobs and policy concessions on electoral reform, control orders, income tax and student fees. He put his own leadership on the line by bonding close to Cameron, making the best of what is normally an awkward partnership. But then any other strategy would have been far worse: either a deal with Gordon Brown or a Commons voting pact with Cameron that would have led to massacre at a repeat general election. In truth, Clegg was trapped.

But Clegg needed more than careful positioning. He needed the hide of a rhino. It was a racing certainty that he would act as lightning conductor for the disappointment and rage of the centre-left. From Cameron it would always be heads I win, tails you lose. From Labour it would be one long howl of anger. The Liberals were Labour's ancestors on the left. They were supposedly Labour in sandals, Labour in suburbs, castrated Labour, wimps' Labour, but somehow half-Labour. Here they were in bed with the Tories. It was treason of a high order.

If there is one thing Britain's left does well it is hatred. Look at the venom Labour directed at the Social Democrats in the early 1980s. Ed Miliband derides Clegg as "a tragic figure". To John Prescott he is Jedward in The X Factor. He has proved so toxic that a Labour invitation to share a platform on electoral reform had to be rescinded for fear of a riot. To the students, Clegg is beyond redemption, a man who cannot keep his promises. This is despite the fact that he and Vince Cable have succeeded in replacing student fees with a graduate tax, which is Labour policy. University fees are a classic of mishandling, political mendacity and misrepresentation. Students are protesting not against fees, which no longer exist, but against a social mobility tax. But the issue will caricature Clegg for life, as school milk did Margaret Thatcher.

A minister with a thin skin is an accident waiting to happen. Clegg's wail that "if you wake up in the morning worrying about the press, you would go completely potty" suggests that he does indeed wake up worrying. John Major suffered the same syndrome. For all the efforts of his staff, he could not kick the habit of reading the midnight first editions, a sure recipe for a sleep tormented by hobgoblins and foul fiends. If the press ever lets ministers rest content at night we are all doomed.

I assume Clegg dislikes cartoons of himself as Cameron's puppet on a string. How does he think his predecessor, David Steel, felt about being drawn literally in David Owen's pocket; or John Major, with his underpants outside his trousers; or Tony Blair, with one eye swivelled and clearly bonkers? He should take advice from such old pros as Michael Heseltine or Kenneth Baker. If you want to survive in this jungle you keep swinging from the branches and roaring with laughter.

Abuse is the small change of politics and these days it is pretty mild. On being told that a cabinet colleague was "his own worst enemy", Bevin famously said: "Not while I'm alive, he isn't." The story was no sooner told than it was re-ascribed to half the cabinet. Matthew Parris's dictionary of political scorn leaves me marvelling at the moderation of Clegg's critics. Where is today's "dessicated calculating machine … ignorant twat … arrogant little shit … semi-house-trained polecat … side-dish I never ordered." Who now jeers, as Disraeli did of Gladstone: "If he fell into the Thames it would be a misfortune; if he were pulled out it would be a calamity"? What equals Neil Kinnock's riposte when Heseltine said he inhabited the gutter: "If I were in the gutter, he would be looking up at me from the sewer"?

All Clegg has to put up with is Harriet Harman saying he has "betrayed a whole generation". It is hardly worth a shrug. If I were Clegg I would breathe in the summer air and skip lightly through the daffodils. But I fear he is, at heart, a Liberal Democrat. The kitchen of power is too hot after the conservatory of opposition. He must shed a tear when he recalls the boudoirs of Brussels, where his sensibilities were massaged by the soft kisses of a million disembodied taxpayers.

• The following correction was printed in the Guardian's Corrections and clarifications column, Saturday 9 April 2011. Listing some prime bits of political invective, a column included Aneurin Bevan's barb 'desiccated calculating machine' – but went astray by spelling it dessicated. Desiccated: from the Latin siccus, dry.