The point to take away from that is that they haven’t been off by 6 points in a two way race. There were large margins in 1948 and 1992 but those were both three way races. There is no national third party to throw off the polling the way Perot did in 1992.
Still waiting to see dramatic shift to 2-3 points after last debate to show “sudden surge” to Obama,since they aren’t showing any internals