Basically, the gist of the game was that when you were with a group of friends, at any random time, a member of the group would stick their finger to their ear, as if receiving a message. Eventually, others would notice and copy the movement, and whoever was last upon sticking a finger to the ear or hadn't noticed gets tackled to the ground regardless of location, and the others would yell "Get down Mr. President!!"
Bob: We played Get Down Mr. President! downtown yesterday. We almost got hit by a car.