While Panagakis found a fairly robust advantage for challengers in the division of undecided voters in 1989, a study by Chris Bowers in 2004 shows a trend of increasing gains for incumbents.

As Figure 1 shows, between 1976 and 1988, undecided voters broke by a margin of four to one. Between 2000 and 2004, this margin declined to about three to two. Bowers attributes the narrowing gap to increasingly ideological political parties. He argues that the difference in parties is “becoming starker,” and, as a result, “more people have made up their minds going into the booth.”

Despite this apparent change, both the Panagakis and Bowers studies demonstrate an overall tendency of challengers to gain most of the undecided voters in the final weeks of an election. While providing valuable insight into the general nature of undecided voter allocation, however, the Panagakis and Bowers studies do not pay substantial attention to the affects of factors such as partisanship on undecided voter decisions. In this study, I expand upon the earlier ones by both updating the findings to include the 2006 elections and by examining the effect of partisanship on the “incumbency rule.”

The first step is to examine the elections in 2004 and 2006 by the same standards used by Panagakis and Bowers in their earlier studies. Both Panagakis and Bowers tallied which candidate (incumbent or challenger) won the greater share of the undecided votes during the elections they examined.

Drawing poll results from Real Clear Politics and The Polling Report, I began by subtracting the final averaged poll results from senate and gubernatorial polls for the incumbent from the actual election result for the incumbent to determine the total number of points the incumbents gained from the final poll until the election. Polls included in this measure had at least one day of the polling period occur during the seven days before the election. I performed the same calculations for the challengers

Next, I added the totals from these two steps and divided the result back into the incumbent and challenger totals in order to calculate the percentage of unallocated voters for each category.

As can be seen in Figure 2, the 2004 results conform very closely to the averages Bowers found for races between 2000 and 2004. More specifically, the incumbent candidate took 41 percent of undecided votes in this study, compared to 40 percent in 2000 and 41 percent in the combined 2002 and 2004 elections. In 2006, however, there was a substantial increase in the performance of incumbents with regard to undecideds, with candidates in office taking almost half of unallocated voters from the preelection polls. This 49 percent incumbent result was the highest found in any of the studies, and marked a noticeable shift from the earlier election periods studied by Panagakis and Bowers.