2008 Presidential Election Status (Compared with 2004)

In the preceding post, I discussed the commanding lead that Obama has sustained and alluded to a changing electoral landscape in which (at least this time) the outcome will not simply hang on the results in FL, OH, and PA.

To provide context for where things were immediately before the 2004 election, I decided to dig up state polling data from Real Clear Politics.  This page gives the RCP Average polling margin for 18 states (those states for which the race was somewhat tighter) in the 2004 election.  Those states were FL, OH, PA, WI, IA, MN, MI, MO, NM, NV, CO, NH, ME, WV, OR, NJ, AR, and HI.

Below is a histogram of the margin of error.  Negative values indicate states where Bush polled ahead of the actual result and vice-versa for positive values.

From this we can see that the RCP Average was generally pretty accurate, with the notable exception of HI (far left of the histogram) which RCP predicted for Bush by 0.9 points but Kerry won by 9.

Since not all states have equal value, I decided to normalize these errors based on electoral votes to give a theoretical RCP error impact (simply, percent margin * state electoral votes)

Again, we see no major bias in the data, with the average theoretical error impact near zero (0.07) and the cumulative error impact is 1.32.  This indicates that the polling theoretically overestimated Kerry's electoral vote total by 1.32 votes.  This positive value is almost entirely due to FL which was polling at Bush +0.6 but was won by Bush with a margin of +5.  Of course this error did not affect the outcome in FL,  so it is important to not misinterpret these theoretical error impact scores as reflecting actual differences in electoral votes.  In fact, there were only two states for which the polling data chose the wrong winner:  HI (4 EV) and WI (10 EV), Kerry won both and they were predicted for Bush.  While polling for HI was way off (see above), the RCP Average for WI was Bush by 0.9 while Kerry won it by 0.4.  Although the outcome was wrong, the RCP Average was still somewhat accurate.  Together the actual impact of Polling error was therefore Kerry +14 EVs.

So what did the polls look like in 2004?  Below is a histogram of the state margins (Kerry - Bush) based on the RCP Averages for 18 competitive states just prior to the election:

The average margin in 2004 for these states was in slightly in favor of Bush by 0.3889 percent.  Kerry led in the polls of 7 while Bush was ahead in 11.  Again, because these states have different EV values, the predicted electoral vote count among these 18 states was: Bush 109, Kerry 78.  The actual outcome for these states was: Bush 95, Kerry 92, a large enough margin for Bush to still win the election.

Below is a histogram of the same 18 states indicating the current RCP Average margin for the 2008 election (Note: states like VA and NC, which may flip to the democrats this year were not among those included in the 2004 list of 18 and are therefore not included here either.

One obvious difference between this histogram and the one above is a rightward shift in polling margin to an average Obama lead by >9 %.  Based on state electoral vote values, this predicts that of the 18 states Obama wins all but two of them, receiving an amazing 176 electoral votes to McCain's 11.

In summary, the 2004 polling data indicates RCP Averages are pretty close to the actual results.

If the current pattern, or anything close to it holds up for the 2008 election, Obama will win far more than the 270 EVs he needs, with a high probability for a landslide.