The Park Service used to estimate crowds for various gatherings, demonstrations, ect. They quit doing that. I am not a big fan of the Park Service, but they got it from both sides when they gave out the numbers.
The spin will begin as soon as the first folks show up before dawn. All the local stations will have some junior reporter standing in the middle of Constitution Ave. spouting nonsense. It always happens. My advice to folkd from out of town is to ignore the TV people.
I understood that they stopped doing it when they exposed the “Million Man March” to be woefully under that number.