Rupert Cornwell: In praise of the redoubtable Mrs Sanford

Some scandals involving sex and American politicians make you cringe – for instance John Edwards' infidelity while running for the 2008 Democratic presidential nomination, at a time when his wife was battling cancer. Others astonish by their hypocrisy, as when Eliot Spitzer, sanctimonious governor of New York and high-minded scourge of Wall Street, was caught last year patronising a high-priced call girl.

But this one is a scandal with a difference. It features an exotic mistress, a politician who seems to have done it for love and who, when found out, confesses all in a rambling stream of consciousness on national TV, and a spouse who has rewritten the script for wronged women. Welcome to the remarkable tale of Mark Sanford, the governor of the state of South Carolina, his Argentinian paramour, and his redoubtable wife Jenny.

The first inkling of it came on (when else) Father's Day weekend in June when the governor went Awol. First it was believed he had taken himself off to do some writing. Then his aides claimed he was taking a therapeutic solitary hike in the Appalachians, while Jenny Sanford told reporters she didn't have a clue where he was. Soon the bizarre truth came out. Sanford had been on a five-day tryst in Buenos Aires with a glamorous former journalist named Maria Belen Chapur.

At that point, in scandals of the genre, events normally follow a set course. The errant politician emerges to read a short statement acknowledging his betrayal. At his side stands the humiliated wife, her face set in a rigor mortis smile. No questions are taken, least of all the only one that matters: will this demeaning rite of repentance save his career? But the Sanfords have broken all the rules. First, the governor admitted the affair at a quite surreal press conference at the South Carolina state house. "I'm a bottom-line kind of guy," he told reporters that day. "I lay it out. It's going to hurt, and we'll let the chips fall where they may."

Second, his wife wasn't there. Instead, she issued a trenchant statement of her own, declaring that her husband's career "is not a concern of mine" (even though it was almost certainly aimed at a presidential run in 2012). "He's going to have to worry about that, and I'm going to worry about my family." That is not how wronged political wives are supposed to behave. Back in 1992, when Bill Clinton's infidelity with Gennifer Flowers hit the headlines, Hillary declared she was not of a "stand by my man" woman – only to behave in precisely that fashion, as she appeared with Bill in a TV interview. Half a dozen years later, she at first dismissed the Monica Lewinsky allegations as part of a right-wing conspiracy.

On 10 March 2008, Silda Spitzer bit her lip and stood next to her man when Eliot appeared before the cameras to apologise for "acting in a way that violates my obligations to my family". But those weasel words could not save him; a week later he resigned as governor. Elizabeth Edwards conducted herself in much the same way. True, she has recently published Resilience, a part-cloying, part-vengeful memoir recounting her battle with cancer and her shock at her husband's infidelity. But it only makes one wonder why she didn't show that shock back in 2007, instead of going along with a deception in order not to upset his political career.

Most recent of all is the case of John Ensign, a family-values Republican senator from Nevada, who last month confessed to an affair with a campaign staffer. Like Sanford, Ensign was mulling a White House bid, and his wife, Darlene, did her best to keep that flickering hope alive. Her marriage had become "stronger" after the affair, she said in a statement, concluding "I love my husband." End of story, or so the Ensigns hope.

But in the Sanford saga no end is yet in sight. Tender emails between the governor and his mistress came to light, proving that love letters are not a vanished art form. In an interview with the Associated Press last week, Sanford went further still. He would die knowing that in Maria he had met his "soulmate". Their liaison was "more than a simple affair. This was a love story – a forbidden one, a tragic one, but at the end of the day a love story".

Within 48 hours, Mrs Sanford had an answer for that as well. Her husband's behaviour had been "inexcusable". Actions had consequences, she warned, "and he will be dealing with those consequences for a long while". Even so, she was willing to forgive him, quoting Archbishop Desmond Tutu's definition of forgiveness as "the grace by which you enable the other person to get up with dignity, to begin anew". Their marriage, she said, might yet be saved. The question now is whether South Carolina's voters will be as magnanimous.

The only person to emerge with an enhanced reputation is Jenny Sanford. Her talents and her self-discipline had never been in doubt. Since 1994, she has combined the duties of a mother with running her husband's victorious political campaigns, first as congressman then as governor. Before that, she was an investment banker on Wall Street. Now she is a feminist heroine as well. In a wife's most trying moment, she has shown firmness without vindictiveness, generosity of spirit without submission. The handling of political sex scandals here may never be quite the same again.