He could have been the first Jewish President

Instead of Barack Obama, it could have been Eliot Spitzer sitting in the Oval Office right now.

As Attorney General of New York state and then as Governor, Spitzer declared a crackdown on the very bankers who were the cause of the global recession, targeting their bonus culture, and proclaiming himself the "Sheriff of Wall Street".

His campaign made the hero of liberal America, and a serious contender for the Democrat nomination for the 2008 presidential election. He seemed destined for the White House - the first Jewish President of the United States.

And then it all came crashing down. Spitzer was ensnared in a Federal investigation into prostitution. An affidavit was released, his identity uncovered and his political career shot to bits overnight. "You're about to watch a Greek tragedy," he said to an aide the day the news broke.

Spitzer, married with three children and very willing to hold himself up as a higher moral power, had been using high-end prostitutes for years. He resigned with his wife by his side.

Now, for the first time he has been talking about the scandal, in a new documentary, Client 9: The Rise and Fall of Eliot Spitzer, by Oscar-winning director Alex Gibney.

"Everyone was talking about the scandal for all sorts of reasons - political reasons, cultural reasons, emotional and sexual reasons," says Gibney. "It just provoked so much debate. It was such a shocker because Spitzer seemed so straight-laced, so much on the right side."

Raised in an observant Jewish household in an affluent part of the Bronx, Spitzer had the best education America can offer - Horace Mann in New York, Princeton, Harvard Law School. He spent less than two years in private law before joining Manhattan District Attorney's office.

His career from there was meteoric - he was elected New York Attorney General in 1998, and was inaugurated Governor of the state in 2007. Using long overlooked laws he took on New York's biggest financial companies. He seemed, in his press conferences and editorials, to predict the financial crash long before it took place.

"If you succeed all the time, you're probably picking battles that are too easy," he said, eagerly sticking his nose where it was not wanted. As a result, he became hated and feared in the boardrooms of Wall Street and the most talked about name in a resurgent Democratic Party.

Gibney, whose films include Enron: Smartest Guys in the Room, about the infamous collapse of the huge Texas energy company, says that much of the Spitzer story has up to now been left untold, and that the man himself has never been provided with an opportunity to explain his actions.

"It was peculiar. You assume a story like this has been covered head to toe, but you begin to start digging and you realise people miss a lot of stuff."

In the film, Gibney interviews Spitzer at length. Discussing the decisions he made as Governor, the fallen politician comes across as an impressive figure with a superb command of his brief. But when Gibney asks him directly, "So why did you use hookers?" his composure falls apart. He seems at a loss to understand it himself. "I gave into temptation," he offers.

Gibney says: "I felt sympathetic towards him, but I had to ask those questions. I felt sympathetic because of what he had done, particularly as Attorney General. I didn't feel sympathetic towards him considering how he had let so many people down that were depending on him.

"But the fact is, if you look at a lot of the interviews in this film, there are a lot of lies told. There are a lot of people looking straight at the camera and lying.

"Spitzer didn't do that, but I don't think he was ever that revealing. What's revealing is his discomfort, because he is so articulate when talking about the political economy. But suddenly when he's talking about this stuff, he's nervous, he's halting, he's inarticulate. You can see what's going on behind the mask.

You can see it in his eyes, you can see it in his discomfort, you can see it in the way he winces sometimes, in the halting way he talks in comparison to the way he talks about the halcyon days of his crusading efforts as Attorney General. I wanted to embrace those contradictions."

Gibney notes that a few months after Spitzer's resignation, the bankers he had policed bought the country's economic system close to collapse and sparked a worldwide crisis - the same bankers who, tellingly, on the day the scandal broke, were cracking open bottles of champagne on the trading-room floors.