It is just a term that means they are entering the race. I imagine that at some time there was a contest and whoever wanted to compete had to throw their hat into the ring or on the table, or into a pile.
To expel a member, two thirds of the House or Senate must agree to the removal.
Error on the throw
Throw the paper ball at him a few times and then eventually he will get red and throw it at him again and he will catch it and throw it back to you.
Because The teacher will send you to the Principal's office if you throw things across the classroom.
throw the golfball at the poster
Throw a grenade in is face
A person that does not consistently vote for one party or the other. Swing states are those with uncertain party loyalty and leadership that can throw their support to a candidate from either political party.
Throw the brain at him untill he catches it. :)
You throw paper past him until he does the signal
Throw the plunger on the top of his head!
Throw a granade on top of it
Use the stapler and when he is facing you throw it