Here’s how NBC News calls races on election night, the steps it takes to verify results and the answers to some frequently asked questions.
How does NBC News project the outcomes of races?
Early on election night, the NBC News Decision Desk uses exit poll data to determine whether uncompetitive races can be called. Most races are called based on analyses of precinct- and county-level vote returns. The analyses also examine differences between early and Election Day votes. In close contests, a careful analysis of how much of the vote has not been counted is a crucial part of the process. No race is projected until the Decision Desk is at a minimum 99.5% confident of the winner.
NBC News will not project a winner in a race until after the last scheduled poll-closing time in a state.
What kinds of calls and characterizations does the Decision Desk make?
Here are the key Decision Desk calls and characterizations our audience can expect to hear from NBC News on election night:
Too early to call: This characterization covers two scenarios. The first is that there might be a significant margin for one of the candidates, but we have not yet met our statistical standards to project the race. The second is that there is not enough data to determine the margin with certainty.
Too close to call: The final margin between the candidates will be less than 5 percentage points. The Decision Desk will not use this characterization until we have statistical confidence that the race will be this close.
Projected winner: NBC News has made a projection that a candidate will win the race.
Apparent winner: NBC News has projected that a candidate has won the race, but the results are close enough that the outcome may depend on a potential recount and/or confirmation that the results that have been reported are accurate.
How will NBC News call control of the Senate?
When a party has gained a majority of seats in the Senate, the Decision Desk will project control for that party.
What is the House Estimate, and how will NBC News project control of the chamber?
The House Estimate is a projection of the makeup of the House of Representatives as a whole. The Decision Desk calculates the probability of a Democratic or Republican victory in each of the 435 House races based on pre-election research. On election night, election analysts examine all the available vote data and adjust the probabilities for every House seat that changes from its pre-election probability. The model then calculates the most probable outcome of the election in the House and an estimate of the probability of error expressed as plus or minus a number of seats.
NBC News is part of the National Election Pool. What does that mean?
The National Election Pool, or NEP, is a consortium of major news networks — ABC, CBS, CNN and NBC — that pools resources to gather vote data and exit poll data. The NEP works with the consumer research firm Edison Research to collect timely and comprehensive election data on Election Day and in the following days, weeks and months until results are certified by all states. The NEP licenses data to several news outlets, including Reuters and The Washington Post.
How are votes counted?
Data reporters across the country talk to local election officials and report raw vote results on a county-by-county basis from the time polls open until they close and long afterward. The data is also collected through state and county vote computer feeds and websites when it is available.
What is an exit poll, and why does it matter?
Using probability-based sampling methods, the exit poll is a survey of voters conducted as they leave their polling places. It is the only survey measure of real voters, and it is conducted at hundreds of polling places. In-person Election Day voters will be interviewed as they leave their polling places. The exit poll also includes extensive interviews with in-person early voters and telephone surveys of early and absentee voters. About 21,000 interviews will be conducted.
What are the steps taken to gather and report election data to make a call?
1. Data reporters and interviewers in the field collect the results.
On Election Day, votes will be tabulated in all 50 states for statewide races, ballot measures and all 435 House races. Interviewers also conduct in-person national and state exit polls, the only survey of real voters in the country, measuring who voted and why they made their choices. About 2,500 interviewers will be working for us through the NEP to collect county- and precinct-level votes and to conduct exit polls.
2. Multiple sources provide vote results throughout Election Day.
Data is collected through multiple sources on Election Day, with data reporters and interviewers across the country calling in results on a timely and rolling basis all day long. Vote data is also collected through state and county websites and feeds.
3. Data is checked for accuracy.
Vote results are rigorously checked and verified. Part of quality control involves checking that vote data is consistent across sources, and we also compare the vote to past election results to see whether the turnout looks extremely different across multiple past races. The Decision Desk vote count analysts, along with computer software, trigger quality control alerts, and senior team members review any votes that fail the quality control check.
4. NBC News independently analyzes the data.
NBC News race projections are completely independent of those of other news outlets. The Decision Desk independently analyzes vote data and exit poll data and uses proprietary statistical models, as well as a team of experts, most with Ph.D.s, in data analytics, polling, election administration and political science to interpret the results to decide when races can be projected.
5. Results and projections are delivered quickly.
Election Day vote data is made available as quickly as possible. Vote counting will continue in several states for multiple days. Exit poll results are independently analyzed in real time, and NBC News calls all races as soon as the Decision Desk is at least 99.5% confident in projections.