Or, to put the question another way, which is the most mesmerising family in American politics?

The Kennedys, you might say, given the fuss over the recent book by the former White House intern Mimi Alford about her affair with JFK. Or you might pick the Obamas.

But no. In terms of their grip on the public imagination, their star power and their enduring relevance, none quite match Bill and Hillary Clinton.

Right now, the spotlight is on Hillary. She is universally considered to have been an excellent Secretary of State.

A presidential run in 2012 is out of the question, and so surely is one in 2016, when she will be 69. But some Democrats still fantasise about an Obama-Clinton dream ticket for November.

In a month or two, we'll have the answer. But Bill's return to primetime is already upon us.

PBS is this week unveiling Clinton, a four-hour examination of the life of the 42nd president, on its flagship documentary series American Experience.

Of course, any decent soap needs plenty of plot twists and plenty of flesh - and Bill Clinton's life provides both in abundance.

Ask anyone to sum up his presidency in two words and all but certainly they would be 'Monica Lewinsky', the White House intern with whom he conducted his own squalid liaison. Part one of Clinton starts with a flash forward to the Lewinsky affair, while the second episode is largely given over to it. But, with Bill, no reverse was ever permanent.

His ability to get himself into trouble was exceeded only by his capacity for getting out of trouble - almost as if he were bored by a 'normal' super-successful existence.

Republicans were driven crazy by their inability to nail him. All but the last two of Bill Clinton's eight years in office were studded by scandal.

And then there were the 'bimbos', whose favours he sought and secured only too often. Bill must be the most investigated president of modern times. Even so, he left office with the highest approval rating of any president since the Second World War.

In a sense, American Experience consigns him to history; indeed, the Clinton era, with its prosperity and balanced budgets, in the interlude between the collapse of Communism and 9/11, already feels like a vanished age, as remote as Downton Abbey.

But the man himself is very much with us, an elder statesman of only 65 whose greatest asset is his own charisma.

In the past fortnight alone he has chaired an 'Invest in Ireland' meeting in New York, held forth on the violence in Nigeria and attended a pro-am golf tournament in Colombia. And, like Hillary, he's also been mentioned for the job as head of the World Bank.

If his wife ever did make another presidential run, would Americans really want another Clinton psychodrama in the White House, even with the roles reversed?

Well, maybe they would. Through all the ups and downs, all the scandals, the Clinton marriage has survived, its partners as mesmerising as ever.