You shouldn't register your cell phone number with the DNC list. That will just give out your number. It is illegal to make a telemarketing call to a cell phone anyway, so the only telemarketers that will call are those that don't mind breaking the law anyway.
Of course, this call was a survey so it's exempt, though I'm suspicious of surveys. If it's the AFL-CIO as you say, then I don't want them to know that I oppose my incumbent Congressman, who is in their pocket and doesn't mind spending billions on fighter jets that the Air Force doesn't even want while our roads and bridges are crumbling.
Nearly ALL telemarketers use robodialers that dial all possible numbers for an area code and exchange. They don't need a list of numbers they just dial all possible numbers.
Political survey on congressional elections, Obama, and governor elections. I must have upset them as the last question was a mumbled "2008, 2008 elections" with no further instructions and then the robot said "invalid response."