After months, indeed years, of polls attempting to predict which way people are leaning in the seemingly interminable race for the White House, on Tuesday evening the focus will switch to trying to gauge how people have actually voted. Exit polls will suddenly be the talk of the town as the major television networks attempt to figure out how and why people have cast their vote in polling stations across the country.

In the 2016 election, as was the case for the last three presidential elections, the responsibility will rest with a New-Jersey based firm called Edison Research to collect data that will be at the heart of early projections.

The firm will interview voters at close to 1,000 polling stations, selected as a stratified probability sample in each state. Together with phone surveys of early and absentee voters, it expects to collect date from more than 100,000 people.

Rather than oral interviews, the information will be gathered in the form of a questionnaire.

“One, we try to make the experience of registering your vote on the exit poll as close as we can to registering your vote at the polling place,” Joe Lenski, Edison’s co-founder and executive vice president told the Pew Research Center. “The other reason is that we don’t want to interfere with the election process, and asking people who they voted for as they’re leaving the polling place could be overheard by people going in.”

The questionnaires will not merely ask whether someone voted for Donald Trump or Hillary Clinton, they will also include questions about the demographics of the individual and why they cast their vote a certain way. These questionnaires are drawn up by the National Election Pool, a consortium comprising ABC News, the Associated Press, CBS News, CNN, Fox News and NBC News.

Once the data, together with early vote returns, is scanned, Edison will make projections and transmit them to the media organizations, leaving it in their hands to decide how to proceed with the information.

One of the major issues to overcome is that younger voters are more likely to complete exit polls than their older counterparts. And there have been some notable past discrepancies between exit poll data and the final results.

In 2004, when polling was done by Edison Research in conjunction with Mitofsky International, exit polls showed John Kerry beating George W. Bush by 3 points nationally and taking Florida, which ultimately went to Bush by 5 points. The pattern was similar four years earlier when, in an infamous battle that eventually went the way of Bush after the Supreme Court halted a recount, exit polls showed Al Gore taking Florida.