Sabato’s Crystal Ball’s James E. Campbell says, Getting More Out of the Polls
Political observers have become more sophisticated in their reading of polls in recent years. They know enough now not to read too much into summer polls. Poll leaders in June are not any more likely to win than their opponents who trail them in the summer polls. By the time of the conventions, though, polls become more meaningful. Since 1948, 12 of the 15 candidates leading in the Gallup poll after the conventions have gone on to win the national popular vote, and by late September the poll leaders have a record of 14 wins and one popular vote loss (Tom Dewey in 1948).
There is more to learn about being sophisticated poll readers, however, than knowing when to take polls seriously. If we compare polls at points in the campaign to the eventual vote, it is clear that a poll lead among registered voters at some point in a campaign is not the same thing as the vote lead on Election Day. Poll leads are, however, related to vote leads in a systematic way, more closely related later in the campaign than earlier, but related throughout the campaign. The question is how are they related? How can we draw the maximum information out of the polls rather than reading them as though the percentages that the polls report are the best indications we have of the vote percentages that the candidates will receive?
From examining the polls over the years, I have two recommendations…