What a shame that a contest that has the world gripped, that is transforming international opinion of the United States, that has shown America in its best and most brilliant light, threatens to descend into a pathetic slanging match over race. What a shame for the centre Left, which had everything to cheer about in the stunning choice between, potentially, the first female and the first black president, that they are allowing the contest to slip into an idiotic series of unproven claims about racial bias.

On Monday Hillary Clinton called for a truce reminding everyone that “Senator Obama and I are on the same side”. Hear hear. But how did it come to this?

The thin catalogue of complaints against the Clinton campaign from the Obama campaign were unfounded, manipulative and self-indulgent. At best they called into question the oversensitivity of Mr Obama, at worst they showed him willing to play a divisive race card that is damaging the entire Democratic Party and tarnishing a great and historic electoral contest for the centre Left. The whole episode has convinced me he isn't tough enough for the White House.

For since when has referring to somebody's past admitted drug use - if indeed the Clinton campaign ever intended to do that, which is far from clear - been a racial slur? More racist, I would say, to equate drugs with blacks, and that's what the Obama campaign is doing, not the Clinton one.

As for Mrs Clinton's statement that Martin Luther King's dream of racial equality was realised only when President Johnson managed to get the 1964 Civil Rights Act through Congress? No more than fact, surely; an attack on Mr Obama's lack of experience, certainly, but hardly a slur upon King. Mr Obama's campaign is twisting things so that a comment about any black man is a comment about him, just as any attack on him is an attack on all black people. I ask again: who is playing the race card here?

The thinnest and most whiny complaint of all was the one that insisted Bill Clinton was “racially insensitive” because he said that Mr Obama's claim to have been consistently against the Iraq war was a “fairytale”. I cannot for the life of me see the potential racial slur in that. Even if, as the Obama camp has wildly contended, Mr Clinton meant to suggest that the story of Mr Obama's own candidacy was a fairytale, it still wouldn't be a racial slur. Many people think that it is a fairytale, in the nicest sense. As in a dream. Now who was it who once had one of those?

Mr Obama seems determined to cry “race” whenever anyone attacks him. He has been playing the game carefully, admittedly, allowing spokesmen and leaked memos to speak for him, while publicly denying that he wants to stoke up the race issue. For a candidate who seeks to be beyond race, it is a dangerous game, which perhaps is why on Monday he told a rally: “We share the same goals, we are all Democrats, we all believe in civil rights, we all believe in equal rights”, adding that the Clintons “have historically and consistently been on the right side of civil rights issues. I think they care about the African-American community and they care about all Americans and they want to see equal rights and equal justice in this country”. And he could have added, but didn't: and I do not believe that they are playing the race card, and I believe they are above that - so stop making those claims in my name.

It's a shame because this gripping contest has the potential to transform perceptions of the United States. It could be an enormous boost for the centre Left in particular - unless the Obama and Clinton teams manage to stuff it up. Many attempts have been made in Britain to align Mrs Clinton with Gordon Brown and Mr Obama with David Cameron (not least by Mr Cameron himself). This is wishful thinking on the part of the Tories. What the US contest is actually showing us is a revitalised centre Left, led by these two fascinating figures, a contest with the power to inspire not just America but the world. The first female or the first black president? What a dream. (Or, sorry, is that racist?)

And what does the “five old white men” line-up say of the future of the Right? The flicker of coverage that the Republican contest has received so far in the British papers has given us a glimpse of a group of ageing men with strange religious or bigoted views, along with one really, really old one who seems nonetheless to be the sanest, John McCain. And guess what? The Republican establishment hates him.

Here is the enemy, Mrs Clinton, Mr Obama: these are the bad guys, not you. If the Republican Party has left its voters, then those five candidates are a stark symbol of why. Do they really have no one to represent women, or young people, or ethnic minorities? Instead, we see the world's leading party of the Right so shrunken in its vision, so backward in its outlook, that it thinks fielding the white male old guard (with those weird starchy wives) is a sufficient offer to a multi-ethnic, consumerist, wired-up and informed electorate in the 21st century.

But let's not talk about that; let's talk, as the “race card” memo from the Obama campaign did, about the time that Bill Clinton said he had known some of the greatest figures of the past 100 years, including Nelson Mandela, yet his wife was the one person in the world he would call on in the toughest of times. And let's talk about whether that meant, as the memo put it, that: “Bill Clinton Implied Hillary Clinton Is Stronger Than Nelson Mandela.” Shame on you, Mr Obama; the world expected more.

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