Bellwethers are polls conducted separately from statewide surveys. A bellwether can be a ward, precinct, town, county, or other district that accurately reflects how a state will vote on Election Day. Bellwethers usually change every election cycle due to shifts in the electorate. Bellwethers also differ by the type of elections – a mid-term bellwether is different from a presidential bellwether, or a party primary bellwether.
Perhaps Paleologos's most well-publicized bellwether call was Hillary Clinton to win the New Hampshire Democratic Primary in January of 2008. Every other poll taken showed Barack Obama winning New Hampshire comfortably, and in some cases by wide margins. The New Hampshire towns of Kingston and Sandown both disagreed and predicted Clinton would be the statewide winner in both trials. She won.
As a sister-test to state polls, bellwethers are not designed to predict margins of victory, just outcomes. At Suffolk, David Paleologos has used his bellwether model nationally in party primary, mid-term, statewide, and presidential elections with great success. Paleologos's proprietary bellwether model has an 89% hit rate as of January 1, 2015.