Could be poor screening, and it could be they're now sampling anyone that will finally answer the phone. Muawiyah's earlier point about Caller-ID is valid. If ours indicates "Blocked" or shows "Unknown Caller" from a number we've never called we don't answer.
It just seems like these “pollsters” are doing everything they can to keep Obama competitive. Over estimating Democrat turn out. Including high numbers of registered voters in their polls. Relaxing screening to include registered voters as likely voters.
I think they have a list of those who answered and keep calling them again. Esp. when you know what they said the first time.