But the weight of the evidence, especially when we look at the location of the outbreaks, suggests that the virus is spread through prolonged, close-quarters, indoor exposure to infected people, including pre-symptomatic infected people.

If you bring together 10,000 people from around the country and put them in the VyStar Veterans Memorial Arena in Jacksonville, Florida, to shout and cheer in close quarters to one another for hours on end, three days in a row — and then send them back to all 50 states — it seems you’re running a pretty high risk of significantly spreading the virus. That’s especially true because the crowd of delegates will include hundreds of people over 65 and because Trump has been setting a norm against mask-wearing.

An outdoor rally would allow for more spacing and less particle recirculation. Limiting it to one day would provide fewer occasions for infection and reinfection. Trump could pick the 15 best speakers, line them up in a row, and have one major blockbuster outdoor event.