When you register for a PARTY/or to vote, or unless you give them your e-mail address you will only get info via regular mail. If you go to particular websites, they always ask for your e-mail and probably somewhere in small print you are agreeing to let them forward to other groups.
Sometimes they'll ask only for zip code. I notice too, that I'll get political things specific to California, from my congress people with CA issues, etc. It's a zoo this election cycle that's for sure. MORE than usual e-mail.
TIS