REALPOLITIK: Trevor Royle

In the greater scheme of things - the casualties caused by the surge in Helmand or planes that fall into the sea leaving no survivors - Mark Sanford's sexual shenanigans should barely register on whatever scale measures standards in public behaviour. The governor of South Carolina is a grown man, the object of his lust was also an adult, there was no rape and no passing of money. All that seems to have happened is the classic male failing of thinking with an organ other than his brain.

He is not the first politician to engage in a dalliance and he will not be the last (to add to the shining hour he admitted that Maria Chapur was not the only one with whom he had "crossed the lines"). For all that the US likes to think of itself as a fairly puritan country, all too often prurience is the norm and there has been no shortage of politicians, including presidents, who have been caught with their trousers at half-mast. From Warren Harding's long-term affair with the wife of a best friend to John F Kennedy's serial sexual fumblings, the White House has been a hotbed of presidential licence.

On occasions, the revelations have been gross (Bill Clinton and Monica Lewinsky); on others they have been vaguely pathetic (Franklin D Roosevelt and his secretary Lucy Mercer). What binds them together is the fact that every one of the philandering presidents managed to survive the scandals - Roosevelt and Kennedy because, in an age when the media was more deferential, they were not reported, and Clinton because he was on his way out anyway and the incident with Lewinsky was simply sordid.

However, in Sanford's case there is more to his disgrace than being caught cheating. By taking himself off to Argentina for a few days of latin liaisons, he destroyed whatever trust he might have enjoyed with the electorate of his state.

Consider the matter objectively. He might have kidded himself that he was involved in a "love story" (cue soft lights and gooey music) but the reality is that he lied to his wife and family by claiming to have gone off on a hiking trip in the Appalachians, and then started changing the story - always a mistake.

Then to compound the felony he asked his people to cover for him. If one of his staffers had done that - lied through their teeth and gone AWOL without leaving a contact number - they would have been looking at the US equivalent of a P45. The only saving grace is that there was no misuse of state funds in setting up Sanford's romantic trysts in Argentina and the local cops have no reason to make any deeper investigations.

Even so, it's an all too typical saga of our times. Sanford was not a bad politician and was generally liked in South Carolina, a state which does not have its troubles to seek with unemployment running at 12%, one of the highest averages in the US.

Fellow Republicans thought highly of him, too. There would have been nothing to stop him having a tilt at the presidency in 2012 but that might be beyond him now. It's not just that he was playing away from home, it was that he fell into the trap of failing to understand that there can be no privilege without responsibility.

More than anything else, that's the great political crime of our times. There are far too many politicians who achieve power and then believe that rules are for others, that freed from the necessity of allowing reality to intrude on their delusions they can behave as they like and not as they should. Goodness knows, Sanford's not alone. Just look at our own cheats and swindlers in the palace of Westminster or take a gander at the bizarre goings-on in the court of Silvio Berlusconi, where pimps and prostitutes take precedence over politicians and psephologists. Hardly edifying, is it?

As ever, within the moral shipwreck there are some survivors. First and foremost there is Sanford's wife Jenny, who has behaved with great dignity throughout and has told her erring husband that he has to earn her trust before she will even think of forgiving him. Then there is Sanford himself, who has been exposed for what he is before he aspires to greater things.

Unlike Gary Hart, an earlier adulterer and presidential wannabe, he won't now have to face the indignity of being exposed as a cheat and a liar while running for the highest office in the land. (For the record, in 1988 with a model called Donna Rice, the venue a yacht hilariously called Monkey Business.)