What is it about Al Gore that renders him so admirable and yet simultaneously insufferable? I ask this as he bathes in the glow of a Nobel peace prize, not to mention an Oscar, a bestselling book, and a career worth several pages on Wikipedia: a golden path at Harvard, a decent showing in Vietnam, a Senate seat from Tennessee, a vice-presidency noted for its high-water mark of influence (only eclipsed by his successor, Dick Cheney), and a post-political career that did a huge amount to increase awareness of what is indisputably a grave environmental challenge.

I should really like him, shouldn’t I? Lots of people do. Last week, a full-page advertisement appeared in The New York Times begging him to run for the presidency next year. “Many good and caring candidates are contending for the Democratic nomination,” said the advert. “But none of them has the combination of experience, vision, standing in the world, and political courage that you would bring to the job.”

His film An Inconvenient Truth made a potentially tedious subject interesting for well over an hour. Yes, I could have done without the footage of this corpulent Cassandra hauling his luggage-on-wheels to another global destination. But his case – that human-created carbon dioxide is dangerous to the planet – is largely persuasive and overdue. His decision to highlight the possible exponential curve of climate change, because of the warming feedback loop caused by receding polar ice, was prescient and alarming in exactly the right way. It hit home more than any number of reports from the Intergovernmental Panel on Climate Change.

And yet - here is the rub – the movie was also undermined by its own self-righteous excesses. You didn’t really need to do much home-work to detect where. Those images of New York flooding – and ground zero disappearing under water – felt like gratuitous agitprop the moment you saw them.

At the High Court in London last week, in ruling that, due to a number of errors, the film should only be shown in schools accompanied by government guidance notes, Justice Burton said: “The armageddon scenario he predicts, in so far as it suggests that sea level rises of seven metres might occur in the immediate future, is not in line with the scientific consensus.”

You think? The same type of exaggeration held on such arcane issues as the drying of Lake Chad, the future of the Gulf Stream, and the drowning of polar bears. These little excesses were larded into the film superfluously. No, he’s not Michael Moore, purveying obvious flimflam for effect. But neither is he the picture of scientific sobriety his image and the movie’sreputa-tion depended on. An air of self- serving sanctimony crept in – and helped undermine the entire project.

It reminded me of his presidential campaign, hard though I’ve tried to obliterate it from my consciousness. By any objective measure, it should have been a landslide. He inherited a booming economy, was an incumbent vice-president, and the world and America were at peace. His opponent, some of us have only belatedly realised, was a mediocre and incurious figure whose grasp of a few fundamentals and genial manner did not, in the end, qualify him to be a global leader in a period of historical crisis.

By any standard of campaigns in 20th-century America, the fundamentals foretold at least a 10-point victory. All Gore had to do was present himself as a continuation of Bill Clinton without any more bimbo eruptions and he would have cruised to victory.

But Gore knew better. He refused to use Bill Clinton on the stump; he veered in the summer of 2000 towards a populism, inspired by the political consultant Bob Shrum, that undid a career of studied centrism; and he harrumphed and sighed his way through the key debates with his opponent. He still won the popular vote by a whisker. And he would have won the entire thing if he had opted for a recount of the entire state of Florida. Instead, he went for a partial recount of cherry-picked Democratic districts and subjected the United States and the world to a bruising and deeply polarising constitutional crisis.

Much of the blame for America’s intense divisions in wartime can be laid at the feet of the men who beat him, George W Bush and Dick Cheney. But the brutal showdown nine months before 9/11 – completely avoidable if Gore had been able to descend from his high horse – was also his responsibility. And its effects continue, even down to the difficulty Hillary Clinton has in persuading anyone outside the Democratic base that she can be trusted with presidential power.

Gore is drawn to the dramatic analysis. It is not enough for the world to be grappling with unprecedented climate change; it has to be six minutes from the apocalypse. It wasn’t enough simply to inherit Bill Clinton’s boom; Gore had to make that election about himself. It wasn’t enough in his recent book to complain about a trivialising media culture; it had to be a full-scale “assault on reason” never before experienced in American history.

I should get over this. Al Gore is essentially right about global warming, and he saw what was coming before anyone else. He could have slunk away into self-pitying isolation after the lost election of 2000; instead he channelled his energies into something constructive. He is extremely smart and diligent. A lot of people wonder if the world would be a very different place today if he’d won the presidency when he should have.

But politics is in the end about more than being correct on the issues. It’s about relating to other human beings, restraining one’s worst instincts at the right moment, and learning how to turn potential foes into allies. Al Gore never managed this after decades of earnestly, painfully trying. He was, in his handsome youth, as one Washing-ton wag put it, every old person’s idea of what a young person should be. And in his maturity, he is every right-thinking academic’s idea of what a president should be. But he has never mastered the core political skills of likeability, empathy and guile that supreme politicians like Bill Clinton or Tony Blair feel in their bones.

That is why we both admire him and dislike him. And why the Nobel prize – given by the experts and the benign – is a far more fitting tribute to him than the leadership of an inexpert, fractious nation. He is the best president America never had – and the best president America never really wanted.

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