I would say that 10% of the government is directly run by demonically possessed people. The rest are just willing servants of their masters, e.g. The FBI and DOJ stooges will do whatever their overlords instruct them to do.
In addition to absolute possession, a person can be demonically influenced, merely oppressed, or partially possessed.
I don't think we are talking about anyone fully possessed to the extent they need an exorcist (though I wouldn't be surprised to learn of such).