Lately, I have been spouting off about how undecideds tend to break about 60% for the challenger and 40% for the incumbent in the final week of the campaign. I was basing this off of a quick estimate from research I had done five weeks ago. However, I had never actually sat down and crunched the numbers to truly determine the average undecided swing in the final week of a campaign in elections involving an incumbent. Now I have, and that is one Friday afternoon and evening that I will never get back.

Using my own research as well as research sent to me by Nick Panagakis of the National Council on Public Polls, I have gone through 451 poll results since 1976. In all 451 cases, the poll was in the field for at least one day that was within seven days of the election. In every case, it was the final poll taken by the polling firm for the campaign in question. Also, I do not believe that any internal or partisan poll results were used. Unfortunately, outside of the Presidential race, I was severely lacking in data from 1996.

My methodology worked as follows:

• 1. Subtract the final poll result for the incumbent from the actual election result for the incumbent to determine the total number of points the incumbent gained from the final poll until the election. Total all 451 of these results to determine the total number of points all incumbents gained from all final polls until the election.
• 2. Subtract the final poll result for the challenger from the actual election result for the challenger to determine the total number of points the challenger gained from the final poll until the election. Total all 451 of these results to determine the total number of points all challenges gained from all final polls until the election.
• 3. Take the total from step #1 and add it to the total from step #2. Divide this total into both the result from step #1 and step #2 to determine the relative gain for the incumbent and the challenger.

The results were as follows:

      
Year	  Polls    Und.    Inc.  Chal. 
President   28	  2.4	 14%	86%
1976-88    155	 11.8	 20%	80%
1994	  101	 11.2	 35%	65%
1998	   76	 10.1	 27%	73%
2000	   31	  8.6	 40%	60%
2002-4	   60	  7.5	 42%	58%
1992-04    283	  8.9	 34%	66%
Total	  451	  9.7	 28%	72%

Here are my first thoughts on this data:

• Is the incumbent rule weakening? With the exception of 1998, where Democrats kicked ass on GOTV, it has been a slow progression toward parity. Then again, this chart has holes, such as a complete lack of polls from 1996, which prevents one from drawing such a conclusion with confidence.

• The number of undecided voters is clearly going down. This year, I see no reason not to expect more of the same. As the two parties slowly become primarily ideological, rather than regional and ethnic coalitions, the difference to voters is becoming starker. As a result of this, more people have made up their minds going into the booth. We really are becoming a polarized nation--that isn't just pundit bullshit.

• The Presidential sample stands out for its extremely small movement from final polls until election night. Even though undecideds break overwhelmingly--better than 6 to 1--in favor of the challenger in a Presidential race, pollsters seem particularly adept at national trial heats in Presidential races. Probably because of the extreme amount of national attention given to the Presidential race, far more people have made up their minds going into the booth than in other elections. While we should not expect significant movement from the final polls on November 1 to the final results on November 2, whatever small movement there is will be almost entirely for Kerry.

• Considering how accurate polling firms tend to be in national elections, in my presidential projections I will now include likely voter models from polling firms that do not include registered voter models. Where available, I will still use the registered voter models until the final week, however. Also, I will only include trial heats that push leaners, and give 80% of the remaining undecided to Kerry. There is simply no way that even 5% of the country will be truly undecided between Bush and Kerry going into the booth.

• Should the 1992-2004 average of 66 to 34 in favor of the challenger, or 2 to 1, be considered a benchmark at which point GOTV efforts make the rest of the difference? At least for now, I'm going to run with this possibility.

It seems like it would be fine to use these numbers as a means of estimating how undecideds will break in any given non-presidential election, as long as it is sold purely as an estimation. These figures are averages and invariably there will be results that break sharply from that average. 66-34 is where the smart money, the house money, should be. You will win over the long term betting on that sort of a split, but in any given wager you might get burned.