For this to be a legit poll, you'd have to ask several follow-up questions: "Did you vote in 2000? For whom? Did you vote in 2002? For whom?" Most pollsters have some method, but at the Ohio Rep. Party, we don't identify a person as a "likely" voter unless he has voted in four consecutive elections. That has worked VERY well for us, as you could see in 2004.
If I made a sale to everyone who promised FOR SURE to buy my products, I would be a multi-millionaire. All salesmen know that if you don't CLOSE the deal right there, you probably WON'T make the sale.