All polls have a RAT bias. And I don't mean an intentional bias; it's just a known fact that all polls taken will end up giving the RATS a few points more "support" than they actually have. They try to factor it out, but usually fail. Nobody's ever pinpointed the reason for this, but I think it's mainly because a lot of people are still afraid to tell anyone they're a Republican, lest they be screeched at, called a racist, etc. So they tell the pollster they're voting RAT, of course they're voting RAT, but then vote GOP in the privacy of the voting booth.
Better known as the "fraud fudge?"