Couric took some heat at the time for asking:

Couric: Harry Truman said, “A man not honorable in his marital relations is not usually honorable in any other.” Some people don’t feel comfortable supporting a candidate who has not remained faithful to his or her spouse. Can you understand their position? Edwards: Of course. I mean, for a lot of Americans, including the family that I grew up with … it’s fundamental to how you judge people and human character: Whether you keep your word, whether you keep what is your ultimate word, which is that you love your spouse, and you’ll stay with them. Couric: Do you think … what about people who use that as a way to evaluate a candidate? In other words, there have been a number of fine presidents according to some analysts … Edwards: Right. Couric: … who have certainly not been sort of exhibited the greatest moral character … Edwards: Right. Couric: … when it comes to infidelity … Edwards: Right. Couric: I guess is what I’m getting at. Edwards: Yes. Couric: So how important do you think it is in the grand scheme of things? Edwards: I think the most important qualities in a president in today’s world are trustworthiness, sincerity, honesty, strength of leadership. And certainly that goes to a part of that. It’s not the whole thing. But it goes to a part of it. Couric: So you think it’s an appropriate way to judge a candidate? Edwards: Yeah. But I don’t think it’s controlling. I mean, I think that, as you point out, there have been American presidents that at least according to the … stories we’ve all heard, that were not faithful, that were in fact good presidents. So I don’t think it controls the issue. But I think it’s certain … something reasonable for people to consider.