Incumbent Rule Redux
Time to revisit "incumbent rule," thanks to Mickey Kaus who highlighted this observation last week by Michael Barone's column in U.S. News & World Report:
It may be time to revise one of the cardinal rules of poll interpretation--that an incumbent is not going to get a higher percentage in an election than he got in the polls. Lieberman was clocked at 41 and 45 percent in recent Quinnipiac polls; he got 48 percent in the primary election. The assumption has been that voters know an incumbent, and any voter who is not for him will vote against him. But the numbers suggest that Lieberman's campaigning over the last weekend may have boosted his numbers-or that the good feelings many Democratic voters have had for him over the years may have overcome their opposition to his stands on Iraq and foreign policy.
I wrote about the incumbent rule quite a bit in the run-up to the 2004 elections (especially here and here), applied it the polls in Ohio and then considered how the rule came up short (here and here). Reconsidering the rule has been buried on my MP to-do list for some time, and while I lack the data to provide conclusive answers, today is as good as any to think out loud about some of the key issues involved.
The best known empirical assessment of this "cardinal" rule was written by Chicago pollster Nick Panagakis for the Polling Report in 1989. He gathered 155 final polls spanning the period from the 1970s to 1988 (though most came from 1986 and 1988) and found that for 82% of the polls, the majority of the undecided broke to the challenger. Note, that this statistic tells us how many polls showed undecideds breaking for challengers, not the proportion of the undecided voters that broke that way.
In September 2004, MyDD's Chris Bowers persuaded Panagakis to share his database and updated it with polls conducted from 1992 to early 2004. Bowers took the process a step further, calculating the average split of the undecided vote over all the elections. He noticed something obviously important in retrospect. The incumbent rule seemed to be weakening (although he had little data from 1996): 80% of the undecided vote broke to challengers in the poll Panagakis collected between 1976 and 1988, but only 60% went to the challenger in the polls Bowers gathered between 1992 and the summer of 2004. And challengers did worst of all in the polls in 2002 and the spring/summer of 2004 (42% to the incumbent, 58% to the challenger).
I have not attempted the same sort of comprehensive review of all of final polls from the fall of 2004, but on the final national presidential surveys an average of roughly 40% of the undecided vote broke toward challenger Kerry. And the break of undecided voters in battleground states looks closer to 50/50. "According to the exit polls," as Slate's David Kenner and Will Saletan pointed out, "Bush got 46 percent of those who made up their minds in the last week of the campaign and 44 percent of those who made up their minds in the final three days."
One question I have wondered about is whether the apparent weakening between the 1980s and 1990s could have been an artifact of the changes in the nature of pre-election polling or the particular races included in the database. For example, did the 1990s see more polling in contests for Senate, Governor and local offices and less in presidential races? Did long term changes in the timing or volume of pre-election polling affect the statistics?
The more important question is why undecided voters have stopped breaking toward challengers in the final week of the campaign. There are many theories.
- One possibility is that post 9/11 politics makes voters more reluctant to take a chance on challengers. Are undecided voters more averse to change given the current emphasis on war and terrorism in our campaigns? Some of the high profile Senate and Gubernatorial races saw a break favoring in incumbents in 2002 (though the incumbents were not exclusively Republican). Consider also this bit of purely anecdotal evidence from MyDD's Matt Stoller:
I phone-banked a bunch of undecideds who in all likelihood flipped to Lieberman in the waning days of the campaign. "I hate the war, I hate Bush, but I'm just not sure we can pull out right now" was the way they put it.
- There is also the alternative theory Barone articulated in his column last week:
The left is noisy, assertive, in your face, quick to declare its passionate support. Voters on the right and in the center may be quieter but then stubbornly resist the instruction of the mainstream media and show up on Election Day and vote Republican, as they did in 2004, or for Lieberman, as some apparently did this week.
- Or could this change reflect a change in the nature of campaigning? Negative television ads were a rarity in the 1970s, but have grown increasingly commonplace in the years since. Has the willingness of incumbents to "go negative" limited the ability of challengers to make the race a referendum on the incumbent and shifted the attention of late breaking voters to the alleged shortcomings of the challengers?
Unfortunately, I have no answers tonight. What is clear is that past trends are not much help in interpreting the pre-election polls of 2006. How the undecideds will "break"in the final days of the 2006 campaign is anyone's guess.