Just a guess.
“There may be one reason we have not considered that prevented Petraeus from taking a polygraph. For all we know Petraeus has been CIA for a long, long time.If so it would have made really good sense to put him in charge of CIA. If so he may have taken numerous polygraphs over the years before the affair.
Just a guess.”
_____________________________________________________
I would not write off any possibility. After Aldrich Ames they were SUPPOSED to have gotten better about following established security/polygraph timelines. If he had been subject to polygraphs for security clearances previously, he SHOULD have been polygraphed every time he came home from an overseas assignment. If he was CIA. Not sure about other agencies.
An affair with a US citizen, as long as he was honest, would not be a red flag, it’s the foreign nationals they’re worried about. I’m more inclined to believe he fessed up during the background investigation (which is why I find the reason he’s offering for his resignation ridiculous), but it’s possible he was not properly investigated because of who he was. If that’s the case, I hope they learn their lesson (again).