As votes are counted on election night and over the following days, the NBC News Decision Desk will be projecting the winners of over 600 races following a meticulous process of data collection and verification. Here’s how that works.

The National Election Pool, a consortium of media outlets that includes NBC News, works with an election data collecting firm called Edison Research to obtain vote counts and conduct the exit polls across counties and states.

Edison Research collects statewide voting results in several ways: from real-time vote tallies on official state and county websites or from “vote reporters” who are dispatched to election offices around the country to obtain vote totals as ballots are counted. That voting data then goes through a rigorous quality check, and NBC News then independently calls each race based on its own analysis of the data. Edison Research and NBC News separately have additional tools to verify the quality of data coming in. (Read more about those processes here.)

Here are the key Decision Desk calls and characterizations you can expect to hear from NBC News on election night:

• Projected winner: The Decision Desk has made a projection that a candidate will win the race.
• If a race is considered too early to call, that means that either there is not enough data to definitively determine the margin, or that a significant margin for one candidate does not yet meet the Decision Desk’s standards for a call.
• If a race is too close to call, that means the final margin in the race is less than 5%. The Decision Desk will not use this characterization until it has statistical confidence that the race will be this close.
• The Decision Desk will issue a leaning characterization when it is confident that the candidate who is ahead is going to win, but the race may take some time before it reaches its standards for a call. 

NBC News only calls a race after the last scheduled statewide poll-closing time in that race, and when it can determine statistically that one candidate’s lead is insurmountable.

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Exit polls, on the other hand, entail surveying voters in person as they leave, or exit, the polling place after they have cast their ballots. For early voters, there is a survey of voters conducted by telephone, text message or email.

Exit polls ask voters which candidates they voted for and which issues motivated them, as well as questions about their demographic background. These surveys are conducted anonymously.

Exit polls can provide a sense of who voted and why before the final votes are tallied. NBC News does not release any exit poll data that characterizes the status of a race until all statewide polls have closed so as to not influence a vote that is still ongoing.

The NBC News Decision Desk also uses exit poll data to determine whether it can project races.