Missed the first few minutes, where it might have been explained, but the rules seemed different from past rules, it seemed to me, where both parties tried to interrupt the other at every possible point that the moderator wasn’t throwing a pail of ice water on him. In contrast, last night, I thought both men were restrained in (as opposed to restrained from) interrupting and fighting for time to speak.
At a guess, I’d say that Lehrer was operating under rules that said, basically, “Through the miracle of modern computers, we will monitor how many seconds you are talking, how many your opponent is talking, and at various points when one of you gets more than a few minutes ahead of your opponent, we’ll give him those few minutes. Each of you will get to talk for the same exact amount of time.”
“I want a nice clean fight, boys. No hitting below the belt. If the other man goes down, go to a neutral corner. Now touch gloves, go back and wait for the bell.”
The general rule was that Lehrer would ask a question and each candidate would have two minutes to respond. Then they would go back and forth on the answers and to challenge the other.
The big difference in this was that the candidates were allowed (hell, actually encouraged) to talk to each other. Usually, the candidate would pretend they were the only one in the room. In this, they could answer the other candidate directly.
There was a point early on where Obama made a point (I don’t recall what it was), and Lehrer said “Why don’t you say that to Senator McCain?”. Obama repeated the point, and McCain asked “What, don’t you think I heard it the first time?”.
There was some back and forth, but you’re right – the candidates tried to ignore each other as much as possible. Lehrer had to practically beg them to address each other directly. Obama did it somewhat, and McCain did it from time to time, but it never became the direct debate the organizers wanted.