What is Nader's game in Wisconsin?

I just got a computerized telephone call asking me to hit phone buttons in answer to a series of questions: would I vote in the coming election, who did I think I'd vote for, and what chance was there that I'd vote for Nader. When I pressed the button indicating "slight or no" for that last question, I was thanked and the call ended. It seems like a pretty efficient way to identify potential Nader voters. Too bad I didn't think of that and pick a different answer on that question so I could monitor what they planned to do with that information.