Soon after polls close and voting in the midterm elections wraps up, election officials across the thousands of jurisdictions in the US will begin to report unofficial results to the media and public.
Every state has its own rules and procedures for how this reporting happens, so news organisations must aggregate data from individual precincts — there are around 176,000 across the US — in each county to ultimately declare winners in these races.
The FT will base its reporting of results on race calls from the Associated Press, which has a team of around 4,000 stringers positioned across the US to log unofficial results as they are released by election officials.
Most counties also post these results on local web sites, which news organisations use to check against on-the-ground reporting.
To make a call on any one race, news organisations must determine whether it is statistically possible for trailing candidates to make up the margin separating them from the leading candidate. Decision desks cross-reference the unofficial results as they come in with extensive demographic and historical data for each state to make these calls.
While many organisations use exit polls, or interviews with voters as they leave polling locations, to power race calls, the AP and Fox News use data from AP VoteCast, a University of Chicago-led survey of about 115,000 registered voters across the country, to declare winners in elections.
If the margin between candidates remains too narrow for decision desk teams to establish a winner, even after initial vote counts are complete, the races are deemed “too close to call”.