For more than a year now, the US political world has expended trillions of person-hours of effort and ploughed billions of words of analysis into assessing whether the United States is ready to elect a black man as president. Countless further words will be written on this same subject before November 4 - and beyond, whether Barack Obama wins or loses. Yet Michelle Obama only had to step up to the speaker’s rostrum in Denver to make it clear, before she even opened her mouth, that there is, and was always going to be, a second question in play in this election, nearly but not quite as important as the first: is America ready to elect a black first lady too?

This isn’t a trivial question. There have been many speeches by African-American politicians at the conventions of both parties down the years - mainly to the Democrats, of course. So the ground has been prepared for the idea that an African-American man would eventually make a presidential nomination acceptance speech one day.

But the ground has not been similarly prepared for an African-American woman to take the audition to be the nation’s first lady. Given all the mystique, the conservative mystique, that surrounds this role - ask Hillary Clinton, 1992-vintage, if you are in any doubt about that - Michelle Obama is at least as much of a pioneer as her husband.

To all but a small audience of political specialists, Michelle Obama is also a total unknown as a person. So she had two tasks to perform in this speech: first to breakdown all the racial stereotypes that still cling to a post like that of first lady and, second, to introduce herself to the electorate in her own right. Any fair judge must surely say that she did the second with fantastic assurance and allure. I also think she cracked it pretty brilliantly with the first question, but it would be naïve not to accept that this will not be easy.

The two questions obviously impact on one another. If America is ready for Michelle Obama, and for the portrayal of Barack Obama that she offered in her speech and in the many videos which dotted the agenda of the first evening of the Democratic convention, then some of the cultural and character questions which make this such a unique election may be answered in the Democratic candidate’s favour. In this context the most interesting thing we learned this evening about Barack Obama is that when he first asked Michelle for a date years ago she turned him down. The Obama charm, in other words, does not carry everything before it after all. It can be resisted. He’s like the rest of us after all. Paradoxically this resistibility helps Obama, because it makes him more human.

To many foreigners, the extent to which the American election process focuses on the candidate’s partner is somehow suspect, proof perhaps of the whole system’s lack of seriousness, in some contexts another snobbish hook on which anti-Americans can hang their coats. Even to many Americans themselves, the idea that the candidate’s wife (as it still has been in all significant cases) has to take a public audition along with her husband certainly is peculiar too. It certainly wasn’t always thus. Until the 20th century indeed, not even the nominated candidate had to make a speech at the convention, never mind his wife. But the presidential audition is nowadays irredeemably a family affair. The wife, the kids, the brothers and sisters, the parents - they all have a role. One can wish it otherwise - but wishing it different won’t make it so.

And by these criteria, Michelle Obama did a hugely skilful job.

She had to persuade the doubters that she wasn’t, as the stereotype has it, another angry black woman. But she did this in a highly principled way, stressing that the struggles of the past were coming to fruition in the Obama candidacy – the pride was unmissable and rightly so – but presenting them in the hegemonic rhetoric of the American dream.

That’s where the current of history meets the new tide of hope, is how she put it, in fluent Obamese, before adding the key line that “That is why I love this country.” That brought the house to its feet. At that moment one knew she had done as well as she possibly could have hoped. It was mission accomplished. Job done - for now.