No ID, unknown number. I never answer such calls. No message. Likely a SCAMMER; I've gotten 3 calls today, one from each of the 3 Phoenix area codes, 623, 602, and now 480 - all the same: No ID, unknown, no message. Friends and other legit contacts know to leave a message. Block if you can.
3rd time is not a charm, SCAMMER. My guess is that whoever is behind these calls is simply phishing for valid numbers - even a valid political survey outfit would identify themselves. Caller ID is a good thing - wait until the number pops up, if you don't know it, don't answer. If everyone did that these calls would stop.