I use to work for Yankelovich Partners who once did the CNN/Time Poll before Harris Interactive took over Yankelovich. Granted it’s been over 10 years ago, but I can tell you their polling is pure sewage and that you’re wasting your time reading a Time/CNN poll. They don’t balance their demographics to get a representative sample based on party I.D. and often over-poll Democrats as a result. My boss who was a raging Dem. didn’t care either that his polls were therefore inaccurate. He was let go long ago for sexual harrassment and racial comments to a black employee. But I doubt things have changed much.
Lots of pollsters do this. There's nothing wrong with that approach. Let the party ID float and you could be wrong. Try to predict the party ID and you could still be wrong. Rasmussen takes something of a hybrid approach between the two. And he could still be wrong.