It's been said before that the list of 'hot topics' is presented to them each morning by their producer(s). The hosts decide together, at their morning meeting, which topics to talk about and which topics don't need to be discussed, and it has to be a majority decision by all hosts. Meghan has sniped about this when she's not happy with a topic. She usually says something like "As I said at our meeting, there are more important things to discuss right now, but I guess you all rather talk about this". (In last year's book "Ladies Who Punch" Rosie said that they could not talk about the legal trouble Cosby was in (2014-15) because Whoopi voted against discussing her friend, and the other hosts sided with her while Rosie did not.)
So as for Toobin, it looks like the majority voted to discuss it before the show. I'm sure if Meghan was there, she'd make her comment that there's more important things to talk about right now days before the election (and she'd be right!).