Secret vote? Not really, anymore
Your actual vote is still secret, at least at most polling places, but politicians are working harder to predict how you will vote. According to the above story in today's Star Tribune of the Twin Cities, politicians are using detailed public and private data to predict how you will vote. If they think you are likely to vote their way, they will phone you, visit you, send brochures to you, and more to make sure you vote on election day.
If you consider this an intrusion on your privacy, you can help make it less profitable for those who practice micro-management of voting. Do whichever of these which suits your personality.
1) If you don't hear a voice when you answer the phone, hang up immediately. You are being called by a machine dialer. You may free a caller up to make the next call, but you are reducing the pool of people they have to talk to.
2) If you didn't hang up fast enough and the caller identifies himself or herself as a solicitor for this or that organization, say something like, "I do not respond to unsolicited calls" and hang up.
3) If you feel opposed to the calling organization, you can possibly get off their list by either asking that you be removed or by saying, "What makes you think I'm interested in your cause?"
4) If you're feeling ornery, you can draw out the conversation as long as possible. This reduces the time the caller will have to talk to other people, reducing the efficiency of this method of getting votes and increase its costs.
You can apply some of these same tactics to pollsters. By not responding you help reduce the accuracy of polls and thus help make a more competitive race. A more competitive race also gives third-party and independent voters a better chance of participating.