Right, I know how it works. I've been following him since he wrote about baseball. But he did tons of stuff about the polling firms themselves. Off the top of my head, I remember Rasmussen generally overstates conservative votes and so on. But has he done that research to the same extent in the UK is what I'm asking.
He would have to, otherwise attempting to make predictions about the outcome would be pointless without weighting the perceived bias of each polling source.