GREG MILLER:Right. Right, exactly, by this—presumably by this author who had written this biography, very glowing account of the general, and spent extensive time with the general in war zones.

RAY SUAREZ:So, these kinds of stories, in another place in the government, in another position in government, would an official be able to ride this out? Is the CIA different from serving in other places in government?

GREG MILLER:Well, you know, even in this case, you have a few voices out there who think Petraeus could have ridden this out.

Sen. Feinstein, the chairman of the Senate Intelligence Committee, issued a statement today saying she doesn't think he needed to resign, although she understands why he did.

But you're right.

I mean, when you are the head of the CIA and you are—have access to some of the nation's most sensitive secrets, and you are caught in a situation in which you could be compromised, blackmailed or somebody else might have access to some of that information, it creates layers of complexity that don't exist for other government officials.

RAY SUAREZ:Professor Mansoor, the president called David Petraeus today one of the greatest flag officers of his generation. Is that a fair assessment?

COL. PETER MANSOOR(RET.), U.S. Army: I think it's fair to say.

He is probably the most accomplished American general at least since the Korean War.

He's done a great deal for his nation. His nation has a great debt of gratitude to David Petraeus for his accomplishments, especially turning around a war that was nearly lost in Iraq in 2007 and 2008.

RAY SUAREZ:Today, the director of national intelligence, James Clapper, said of Petraeus:

"Dave's decision to step down represents the loss of one of our nation's most respected public servants."

Does leaving under this kind of circumstance undermine that title, one of our nation's most respected public servants?

PETER MANSOOR:I'm not so sure.

I think in the long run, his personal failings will be a blip on the record. Certainly, his public service has been exemplary. And he's done, like I said, a great deal for his nation.

He has hunted down war criminals in Bosnia. He's had three combat tours in Iraq. He took over in Afghanistan at a very difficult time, and he's lead the CIA with a fairly deft hand.

So I think, in the long run, his legacy will be one that Americans will remember with fondness.

RAY SUAREZ:Greg Miller, is this a tough time for the CIA to lose its chief under any circumstances, given the continuing questions about events in Benghazi?

GREG MILLER:Yes. And that has already led to a lot of speculation on the timing of this departure by the director.

I mean, this is coming just a couple of days after the election. There are questions about whether—you know, whether the administration knew this was coming.

White House officials insist that wasn't the case and that President Obama was stunned when Petraeus came to him and made clear his intent to resign.

RAY SUAREZ:How has the CIA changed under his leadership?

GREG MILLER:Well, you know, at 14 months, he has been there less time than all but a few other directors. And so I would say a couple things.

I mean, he has presided over a significant expansion of the drone campaign in Yemen, broadening the CIA's drone program beyond Pakistan.

At the same time, he has a reputation for being cautious. Some have questioned whether he has been too reluctant to put agency operatives in conflicts like Syria.

And he has also reportedly clashed with the head of the agency's CounterterrorismCenter over Petraeus deciding to tap the brakes a bit on the drone campaign in Pakistan.

RAY SUAREZ:Professor Mansoor, you know General Petraeus personally, worked side-by-side with him. What should we know about the man to help us understand what he's going through now?

This must be a crushing thing for someone who so carefully cultivated his reputation and made such prodigious use of his talents.

PETER MANSOOR:Well, there's no doubt that he understands this was an unacceptable personal failing.

It is very surprising to those of us who have known him, who have known how driven he is in his professional life, and really how upstanding he's been to this point at any rate in his personal life. He, you know, refused to drink alcohol when he had the opportunity to in Iraq, because the troops couldn't drink alcohol.

He was in every respect the paragon of propriety, at least when I was there for the 15 months. I lived right next door in a bedroom right next door to him.

And, you know, he built his entire career on public service to the nation. He sort of envisioned himself as the modern day George C. Marshall, who after a long career in the U.S. Army became secretary of defense and secretary of state.

This has got to be a severe blow to General Petraeus. And our thoughts and prayer goes out to him and his family in this time of healing, hopefully.

RAY SUAREZ:Greg Miller, finally, before we go tonight, the president expressed the hope that the agency would continue to thrive under the new acting director, Michael Morell, who has been the deputy director under General Petraeus. What you can tell about him—tell us about him?

GREG MILLER:Morell is a sharp guy. He is a professorial figure. He comes from the analytic side of the agency, not the operations side. So he has risen through the ranks on the analytic side, was a briefer to presidents and is regarded as a highly polished and a highly skilled guy.

In fact, he served as interim director before Petraeus took the job, because Petraeus, it took several months between the transition from Panetta to Petraeus. So, Morell has done the job for a while previously.

RAY SUAREZ:Gentlemen, Greg Miller from The Washington Post, Professor Mansoor, thank you both for joining us.