We’ve seen sex scandals before, but this one hurt.

From the disappearance of South Carolina governor Mark Sanford in 2009 to the collapse of Eliot Spitzer’s political future in 2008 and the obliteration of John Edwards’ genteel Southern morality that same year, Americans have seen it all. From those who politically got away with it (Barney Frank, Newt Gingrich) to those who didn’t (John Ensign, Anthony Weiner) to the mother of them all — Bill Clinton — the political sex scandal is almost quintessentially American.

We’ve seen the best and the worst, the great and the forgettable — the strong and the weak all fall victim to personal disgrace over the years. But for some reason, we didn’t see this one coming.

This week, CIA director and potential political superstar David Petraeus resigned after an FBI investigation revealed he had engaged in an extramarital affair with his biographer.

Petraeus was a war hero — if the Iraq War can have heroes — in a time when America found disappointment after disappointment in its generals. He had a reputation for efficiency, insight and getting to the essence of the problems facing American troops abroad and citizens at home. He was in more ways than one the mastermind behind the successful Iraq troop surge of 2007. Based on his success, he was appointed head of the CIA in September 2011.

And now we’re here. We’ve arrived at the inevitable chaotic end to the story, where Petraeus finally stoops to the level of every other political farce.

Like Sanford — who mysteriously ran off to Argentina for nearly a week while South Carolinians wondered where he went — Petraeus was incredibly thoughtless, almost utterly incompetent in his senselessness. He was the head of “central intelligence,” and yet he fell to the level of the very terrorists and criminals he sought to defeat when he used a Gmail drafts folder to communicate the gritty details of his grotesque obsession with his paramour.

Like Spitzer, he lost control of the fatal flaw he’d managed to keep hidden behind his ambition for so long. He could lead the fight against an insurgency in Afghanistan, but he couldn’t keep his pants zipped shut. He was able to resist the clamoring of his rivals and subordinates for power and attention, but he couldn’t resist the allure of an affair and a shot at a shamelessly flattering biography. And eventually, Petraeus’ double life caught up with him.

This scandal hurt because we tricked ourselves into believing Petraeus was something more than he was. He was Congress’ darling and President Obama’s hand-picked anti-terror expert. He was the leader who corrected the tomfoolery of the generals responsible for getting America into the Iraq quagmire and the face of a more intelligent military future. But when we cut through the hubris and the hollow praise, we realized he was just another flawed leader.

Gen. Douglas MacArthur quoted an old barracks song in in his farewell address when he said “old soldiers never die; they just fade away.”

This soldier sure faded fast.