The New York Times – A closer look at our election forecaster before the Iowa caucuses. “Shortly before 9 p.m. Eastern on Monday, we expect the first returns from the Iowa Democratic caucuses. If you choose to follow the results live tonight, we hope you’ll do it with us: We’ll have results, analysis from our reporters and interactive maps. We’ll also have what we call a live forecast, known to many readers simply as “The Needle.” Below, we’ve provided answers to some common questions about the needle and our plans to use it during the caucuses.

What is the needle? It’s the visual representation of The Times’s live election night forecast. It combines initial election returns with other sources of data to estimate the final result of an election before all the votes have been counted. Before the election, we use polling data, census data and prior election results to come up with a baseline estimate for how every precinct or county will vote. As the results come in, we compare the actual returns with our baseline. We then adjust our expectations for the vote that’s left: If a candidate is running ahead of our pre-election expectations in the areas that are counted, we might assume that he or she is also poised to do better in the demographically similar areas that remain…”

See also Washington Post – How is TV news going to cover the weirdest, most fraught election in history? All of your questions answered.