I’m sure as long as the moderators are fair, i.e. prevent someone like Rubio dumping a load of unassociated and discredited opposition research items on Cruz’s head as the buzzer sounds, then disallow the time it would take to refute each, he’ll do just fine.
You would think this is an outstanding opportunity for Rubio to take Cruz down a couple pegs and get a stronger outcome in Iowa. Considering Cruz has been weak in several of the following states, Rubio could be setting himself up for the 2nd place spot.