Let me remind you again, it's not federal but by state. The polling methodology is suspect as well:
In other words they spam call finding an end run around do not call laws (federal and state). The only people that respond to this are those with strong beliefs one way or the other and have a lot of time on their hands (so conservatives will be under represented ). I've actually been called by these knobs and told them off for violating the DNC list and informed them of the lawsuit I can bring if they call again. Here in Oregon once you inform one of these spam callers to never call again, subsequent calls are actionable.Landline
In the landline component of these surveys, a sample of landline households in the continental United States is selected by SSI via random digit dialing procedures, in which all landline telephone numbers, listed and unlisted, have an equal probability of selection.