"If your email inbox starts overflowing with messages from political campaigns this election season, it could be because your state sold you out. A Fox News study has found 19 states plus the District of Columbia, now ask for an email address on voter registration cards. In nine of those states, email addresses from the cards are then sold to political parties, organizing groups, lawmakers and campaigns who can use them to send unsolicited emails.
States that ask for email addresses on voter registration forms:
Arizona, Arkansas, California, Colorado, District of Columbia, Delaware, Indiana, Iowa, Maryland, Minnesota, Montana, Nebraska, New Jersey, Oregon, Rhode Island, Tennessee, Virginia, Washington, Wisconsin and Wyoming
States that sell email addresses listed on voter registration forms:
Arkansas, California, Indiana, Iowa, Montana, Oregon, New Jersey, Rhode Island and Wisconsin
Note that it is not against the CAN-SPAM act to send unsolicited POLITICAL email. This provision is not (necessarily) because politicians want an exception, it's because of the First Amendment. The courts have uniformly come out against ANY legislation that interferes with political speech.
For instance, a TV station CAN NOT refuse to run a political ad, no matter its contents; naked titties, profanity, whatever, the station MUST air the commercial.