To add onto what Recon said, you also must pay a Union due when you are in a union. Some jobs require you to be in a union. That money that is taken as your due tends to also be used for political donations. You could be funding a candidate that you don't like and would not vote for. Unions had a purpose, and may still have in some sense. But I believe that purpose is waning and a lot of them have become more trouble then they are worth. I have still yet to figure out why we have Unions for government jobs...