snipped from kos...
We're always talking about the 50 percent rule, but it's rarely explained. And given all the new people visiting the site, it's time for a refresher course. I'll steal Mystery Pollster's explanation.The basic idea is that voters make their decisions differently in races involving an incumbent. When newcomers vie to fill an open office, voters tend to compare and contrast the candidates' qualifications, issues positions and personal characteristics in a relatively straightforward way. Elections featuring an incumbent, on the other hand, are as Molyneux puts it, "fundamentally a referendum on the incumbent." Voters will first grapple with the record of the incumbent. Only if they decide to "fire" the incumbent do they begin to evaluate whether the challenger is an acceptable alternative.
Voters typically know incumbents well and have strong opinions about their performance. Challengers are less familiar and invariably fall short on straightforward comparisons of experience and (in the presidential arena) command of foreign policy. Some voters find themselves conflicted -- dissatisfied with the incumbent yet also wary of the challenger -- and may carry that uncertainty through the final days of the campaign and sometimes right into the voting booth. Among the perpetually conflicted, the attitudes about the incumbent are usually more predictive of these conflicted voters' final decision than their lingering doubts about the challenger. Thus, in the campaign's last hours, we tend to see "undecided" voters "break" for the challenger.
That's the theory. Does it have any empirical support?
In 1989, Nick Panagakis, president of Market Shares Corporation (the firm that polls for the Chicago Tribune) analyzed results from 155 surveys, most from the late 1980s, all conducted during the last week before an election. In a famous article in The Polling Report, Panagakis found that
in 82% of the cases, the undecideds "broke" mostly to the challenger.His conclusion? "Incumbent races should not be characterized in terms of point spread.
a poll shows one candidate leading 50% to 40%, with 10% undecided...Since most of the 10 points in the undecided category are likely to go to the challenger, polls are a lot closer than they look - 50% to 40% is likely to become 52% to 48%, on election day" (emphasis added).
Just last month, Chris Bowers of MyDD updated Panagakis' work. Though he found some signs that the incumbent rule might be weakening in state and local races, he found even stronger support for it in presidential elections. In 28 surveys involving presidential elections, 86% showed undecideds breaking mostly to the incumbentchallenger.
Going back to the polling data at 2.004K, it's also interesting to see the number of supposed safe Bush states that are hovering on or just above 50 percent.
Kerry is tantalizingly close to breaking the race wide open and getting the sort of landslide victory that would conclusively repudiate the Bush agenda.
http://www.dailykos.com/story/2004/10/20/104048/91