Are National Polls Reliable Predictors of Midterm Elections?

Source Organization: Pew Research Center


10/26/2006 - National elections are the high season for pollsters and with Election Day now less than two weeks away, new polls on the fight for Congress are being released nearly every day. Commonly, pollsters use something called the "generic ballot" to assess the state of the congressional race. This question measures the percentage of voters in a national survey who say they intend to vote for either the Republican or Democratic candidate for the U.S. House of Representatives in their district. Of course, there is no nationwide election for the House; instead, there are separate races in each of the House's 435 districts. Moreover, over the last decade and a half, the number of truly competitive districts has declined significantly. So it might seem that the generic ballot is too broad a measure to forecast the national outcome; nonetheless, it has repeatedly proven to be an accurate gauge of the two-party national vote in off-year elections, though not necessarily of the final distribution of congressional seats.

The Gallup Organization has tracked voter preferences in House races for more than half a century, and its final midterm election polls have consistently paralleled actual election results. Indeed, on average, the final Gallup Poll has been within 1.1% of the actual vote. Similarly, surveys by the Pew Research Center for the People & the Press (as well as its predecessor, the Times Mirror Center for the People & the Press) have consistently shown that the generic ballot closely tracks election results. For example, in 1994 both the Pew and Gallup surveys found a Republican majority in the popular vote for the first time in more than 40 years, foreshadowing that year's GOP takeover of the House.

Read the full report Are National Polls Reliable Predictors of Midterm Elections? on the Pew Research Center Web site.

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