America has just had what I call a Blazing Saddles moment. You'll remember the scene. The downtrodden townsfolk are desperate for a hero. That old prospector, John "Johnson Johnson" McCain has been talking authentic frontier gibberish. Then over the horizon comes riding the coolest, sharpest dude of a sheriff you are ever liable to see.

At the first the townspeople are beside themselves with relief. Then the ancient quells his gibberish just long enough to put out a singular detail. Sheriff Barack is a ni... Unlike Mel Brooks, we'll settle for African-American. We might add, though, that in some quarters the Democratic candidate for the presidency of the US is about as welcome as Cleavon Little in Rock Ridge.

Is he a "secret Muslim"? Is his patriotism in question because he has sometimes failed to impale himself on one of those stars and stripes lapel badges that are, for American politicians, almost compulsory? Was his taste in preachers not revealing? But here's a better angle for the shock jocks and the lunatic bloggers and Fox News. Doesn't Obama possess an intelligent wife who happens to be capable of speaking her mind?

Oh, she's black, too. In fact, in some quarters she is already being described as "an angry black woman". (Just a thought, but if she's not, Michelle Obama should be). Tasteful types have meanwhile taken to likening the Ivy League-educated lawyer to the candidate's "baby mama". The reference, if you didn't know, is to unmarried mothers and neglectful young black men who fail to live up to their parental duties. Neither slur applies to the Obamas, but what the hell.

Then, famously, there's the fist bump. Or if you prefer the faux-innocent Fox inquiry, the possibly "terrorist-inspired" fist bump. Anyone who thought it was just a gesture of affection between a husband and wife can't understand the dangers America faces. They have also overlooked all the harmless kids, basketball stars, European football players - and George Bush, no less - who are also sleeper agents for Hezbollah.

Race is an issue in the United States, as it is on this side of the Atlantic. America, to its credit, comes down hard on overt expressions of foul sentiment, but the tensions remain. African-Americans, in the main, don't get it easy. More tellingly, whites and blacks don't mix much or often, and a small white minority still can't conceal its hatred of its former slaves. That would be one reason, I think, why Obama was receiving Secret Service protection long before he seemed likely to overcome Hillary Clinton in the primaries. It might also be a reason why Michelle Obama never wanted her husband to run for office.

Yet here's the candidate, nevertheless, who stands in history's ante-room and declares that he will not be defined by his skin colour. Fox, and the bloggers, and the maniacs with microphones, respond: We'll see about that.

The attacks on Michelle Obama have been astonishing on several levels. One shock comes from realising how very few people there are who will name racism for what it is. Democrats and "liberals" seem almost to have internalised the fact that the Republicans and their cheerleaders will always smear and savage when the White House is at stake. In a peculiar way they validate disgusting behaviour by accepting that it is, somehow, par for the course. Michelle Obama is, as one right-wing commentator happily conceded, fair game.

It's two-for-one, after all: racism and sexism without the risks involved in a frontal assault on the candidate. It is almost cost-free, too, if you adopt the habitual tactic of Fox - prop. Rupert Murdoch, lest you'd forgotten - in first airing the smear and then offering the token, half-hearted apology when your "fearless journalism" is misconstrued.

But that's the game. It would be tasteless to bring up the long battle waged against an addiction to pills by John McCain's wife. It would be a cheap shot to talk about her substantial inherited wealth. But allege - without a shred of proof - that a tape exists in which Michelle Obama talks of "whitey" and all denials come too late. Before you know it, the husk of what was once Christopher Hitchens will be trawling through a woman's 1985 college dissertation to uncover the word "separationism". Hasn't anyone in America heard what Hitchens was up to in the eighties?

Mercifully, Obama appears to be capable of standing up for herself. On the strength of a handful of interviews, at least, she seems to be quite as sharp as her husband. Nevertheless, if this is the pattern being set for America's general elections, you can only wonder how long it will be before race and attitudes towards race begin to head the agenda. The attack on Michelle Obama has been notable, after all, for two things: a lack of any substance and utter shamelessness.

Is it because she's an intelligent woman, perhaps too intelligent for the mute, deferential role assigned to the sort of First Lady with whom much of America is comfortable? Hillary Clinton would know all about that. In fact, though you can understand a sense of grievance may still be nurtured among some of the senator's feminist supporters, their current silence is striking. Hillary, they say, was denied her due and subjected to outrageous sexism. There is some truth in the charge, just as there is truth in the allegation that members of the Clinton camp were happy to say that Obama only got this far because he is black.

Even if such people are angry, even if some maintain they will vote for McCain before Obama, wouldn't women, in particular, respond to the calculated abuse of the candidate's wife? She's a black woman: only in exceptional cases do those facts fail to qualify a person as the holder of a short straw. Instead, months on, Obama's "ill-advised" (though not in my book) admission that her pride in America was limited before her husband arrived is still dragged up. Where are we now? Loyalty oaths? A belief that patriotism erases the shared history of slavery? But I forget: Michelle Obama is an "angry black woman".

Not so I've noticed. She strikes me as composed and confident. Pictures of her scowling or ranting have yet to appear. Equally, both she and her husband - who didn't swear his Senate oath on the Koran; nice try - are if anything socially conservative. These are the sort of middle-class professionals who lecture young black men on duty and responsibility. These are not the Black Panthers in tailored suits. But they are black, or of mixed parentage. What they are not is white.

The candidate's ability to steer clear of this issue is going to be tested. That's the strategy. Attack his wife - loving husbands are easily provoked - and do so in terms calculated to make middle America uncomfortable, or more uncomfortable, with the sight of black folks aspiring to the republic's highest office. What truly interests the outsider, however, is a question: are the Obamas to be put through the mill because of politics, or is actual racism bringing this filth to the surface? And is America unable even to broach the subject?

You could recall, of course, that Hillary Clinton fully expected to face a brutal contest had she secured the nomination. Garbage of a different variety - little of it new, and some of it rooted in fact - was being prepared just to keep a woman out of the White House. The treatment of Mrs Obama seems, nevertheless, to be of a different order. She can't say it, but I will: whitey is angry. And the battle has barely begun.

If the polls are to be believed - and national polls in the US are always tricky - the majority isn't having it. With luck, Obama will do more than beat McCain. He'll put the rabid right back in its box, once and for all. The ghost of Joe McCarthy would appreciate the irony. As would the fine folks of Rock Ridge.