Why include the results of the regression analysis at all?
Because polls are an imperfect measure of voter sentiment, subject to the vagaries of small sample size, poor methodology, and transient blips and trends in candidates’ polling averages. For example, the late February Survey USA polls had Barack Obama ahead four points of John McCain in North Dakota, but behind by four points in South Dakota. Since North Dakota and South Dakota are very similar, it is unlikely that there is a true eight-point differential in how Obama polls in each state. The regression estimate is able to sniff out such discrepancies — and so, for example, it recognizes that Obama is in fact an underdog in North Dakota. Put differently, it is a way not to be held hostage by the results of individual polls that might defy common sense, particularly where polling data in a state is sparse.
