You could do it back in the 1940's and early 1960's, but not today with millions of camera-equipped cellphones. Alex Jones--love him or not!--noted very recently that Hillary's campaign rallies have a complete lack of flashes from cellphone/conventional cameras taking pictures, while Trump's campaign rallies have lots of flashes from cellphone/conventional cameras taking pictures. Given that flashing lights can trigger off epileptic seizures if the person is susceptible to such seizures, could this tell us that Hillary is suffering from a serious neurological condition?
The absence indicates that her rank and file supporters know and are down with it...