Polling Report, Incumbent Races: Closer Than They Appear

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How will undecideds vote on election day? Traditionally, there have been two schools of thought about how undecideds in trial heat match-ups will divide up at the ballot box. One is that they will break equally; the other, that they will split in proportion to poll respondents who stated a candidate preference.

But our analysis of 155 polls reveals that, in races that include an incumbent, the traditional answers are wrong. Over 80% of the time, most or all of the undecideds voted for the challenger.

The 155 polls we collected and analyzed were the final polls conducted in each particular race; most were completed within two weeks of election day. They cover both general and primary elections, and Democratic and Republican incumbents. They are predominantly from statewide races, with a few U.S. House, mayoral and county wide contests thrown in. Most are from the 1986 and 1988 elections, although a few stretch back to the 1970s.

The polls we studied included our own surveys, polls provided to us directly by CBS, Gallup, Gordon S. Black Corp., Market Opinion Research, Tarrance Associates, and Mason-Dixon Opinion Research, as well as polls that appeared in The Polling Report.

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http://www.pollingreport.com/incumbent.htm