Re Man wiping lectern before debate:
From the comments and photos, it seems two men fussed with the lectern before the debate: a man in brown boots who wiped it, and a man in jeans who sprayed it. Not sure of order.
Spitballing: the level of infection indicates to me that the virus was airborne. If POTUS infected others, it would have taken a week or two for them to develop symptoms. But POTUS and Christie had matching onset. I still bet on the Rose Garden ceremony, or a meeting that took place prior.
I concur - Rose Garden ceremony or meeting of same time frame. The timing, based on incubation/gestation period lends to that being the infection event.