They won't reveal where the data comes from because they are using publicly funded computers on university campuses nation-wide to gather, hold and coordinate the use of the data during national elections. This is, of course illegal, and I have no way of proving what I say, but I've now spent the majority of my life in a university town in close working relationships with highly committed left-wingers. there are some of these folk whose behavior often betrays the fact that they have knowledge of things they will not discuss. I've spent a lifetime talking to people as a physician, and there's a sixth sense you develop that shows you where certain walls are in a person's psyche. This is why Romney tried to do the ORCA thing.