Trump is campaigning in heavy red zones.
Most of Clinton’s campaign rallies (what there are of them) are held at high school gyms, and college campuses. Yesterday, she was at OH State, it was a holiday on a campus with about 60,000 students, so she did manage to get a respectable (for her, anyway) crowd, but most of her events are under 1,000, and sometimes they have to bus in high school kids to fill up seats.
she does not have to pay for those college auditoriums because it is spun as “educational”.