"Based on what the goal was, I saw it as successful," said Jim Lehrer...

... about his performance as moderator:

"I’ve always said this and finally I had a chance to demonstrate it: The moderator should be seen little and heard even less. It is up to the candidates to ask the follow-up questions and challenge one another."

"I don’t consider that being passive, I consider it being effective... It’s not my job to control the conversation. If the candidates gave me resistance, and I let them talk, to me that’s being an active moderator, not a passive moderator."

I'll endorse that philosophy of moderation.  I remember seeing a debate some years ago — I forget when or who was in it — where 3 — I think it was 3 — candidates sat at a round table and just talked to each other. They had to moderate themselves. It worked well. There are incentives not to dominate the conversation, and I think Obama and Romney would do just fine in that format... which was rather close to what Lehrer allowed them to create for themselves.