If it’s after 5 p.m. Eastern on Election Day, it’s exit poll time! If you’re watching the news or scrolling social media tonight ,you’re likely to encounter findings from this mega-poll of voters throughout the night (and coming weeks). But there are some reasons to take what you see, especially early, with a grain of salt.

The exit poll is a survey of voters nationally and in key states that asks people questions like who they voted for, when they made up their mind and why they voted the way they did. The exit poll is conducted by Edison Research (a survey research, voter data and election returns company) and sponsored by a consortium of news networks in the U.S. (ABC News is one of them.) ABC News will be reporting exit poll results nationally and in 10 states: the seven battleground states (Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin) plus Florida, Ohio and Texas.

Long ago, the exit poll only interviewed people in person as they left their polling places after casting ballots in person on Election Day. With the rise of mail-in and in-person early voting, the pollsters and statisticians behind the exit poll added telephone interviews to account for early and mail-in voters.

The exit poll is an incredible feat of engineering and a rich source of data on voter behavior in America, and you can expect it to be cited frequently after the election as a measure of “ground truth” (or at least one of the highest-quality estimates available) about how and why people voted. However, at the end of the day, the exit poll is just a very detailed survey, so it is not infallible. In particular, the way it is conducted warrants two main caveats:

First, the results of the exit poll can and will change over time, especially at the subgroup level. The earliest results of the exit poll are essentially toplines and crosstabs from a very large poll of voters, but which contain a lot of guesses about the eventual demographic composition of the country. As the votes roll in over the course of the election night (or week), the pollsters behind the scenes adjust the results of the poll to match the results of the election.

As a result, the findings of the exit poll can and do change as more votes are counted, especially for subgroups. In Wisconsin in 2020, for example, preliminary exit poll results had Trump +1 among men. In final data (weighted Wednesday morning), Trump was +10 among men. Overinterpreting the poll — say, if you had hitched your horse to the wagon of low or no gender gap in the electorate — risks setting up narratives that are swiftly knocked down with actual data.

The second word of caution is to remember the exit poll is just one imperfect estimate. Yes, it is generated with a lot of data and care, but misspecified weights or sampling noise can impact results just like with any other poll. Interpretations of the final exit poll results should be used with caution. As a result of all these caveats, 538 rarely cites exit polls, and we prefer to wait for actual results before wedding ourselves to narratives. If you are going to cite the exit poll, we recommend waiting until it has been at least somewhat weighted to be representative of actual election results.

While most Americans don't name climate change policy as their top concern for this election, they do care about it, and majorities want to see the government do something to curb greenhouse gas emissions. But Biden's signature climate change law, the Inflation Reduction Act, and the strident Republican opposition it's incurred, has spurred a decrease in support for climate-related policies among the broader Republican electorate. That's especially true when it comes to one of the most visible components of the law: electric vehicles.

Pushing Americans away from gas-powered vehicles by encouraging EV production and purchases through tax incentives, while raising fuel-efficiency requirements for auto manufacturers, has been one of the primary policies through which Biden has aimed to meet his pledge to cut greenhouse gas emissions in half. In response, opponents accused the president of trying to control what kinds of cars Americans buy, and Trump has railed against electric cars, boats, their batteries and, um, sharks while on the campaign trail.

That may have had an effect. While EV ownership has risen in recent years, the pace of new purchases has slowed. A Pew Research Center survey from June showed a decline in those who would seriously consider buying an electric vehicle: About 29% in the June survey said they would, down from a high of 42% in 2022. Public opinion among Republicans about EVs has cooled across the board, as has their support for other clean energy policies during Biden's presidency: In 2016, 87% of Republicans supported expanding solar power and 80% supported expanding wind, according to Pew. Those numbers have dropped by more than 20 points, to 64% and 56%, respectively, in this year's survey.

Trump has labeled the Inflation Reduction Act wasteful, has promised to pull back unspent federal money for the programs it's meant to fund, and calls the broader climate policy supported by some Democrats, the Green New Deal, the "green new scam." He's also particularly hammered home his opposition to electric vehicles to curry support in Michigan, a key swing state and national auto manufacturing hub. But whether or not the Republican push against EVs will make a difference in the presidential contest tonight, the drop in support for pro-EV policies could have a big impact on the future of clean energy policy.

Back in 2020, we anticipated that some states would see especially pronounced "red shifts" and "blue shifts" in their vote tallies as returns came in through the night. Here in 2024, we can expect at least some of the same, although the picture will differ in some respects.

That is, some batches of votes that are more heavily Republican-leaning may be reported at similar times, and then batches of more Democratic-leaning votes. This has to do with the tendency for Republicans to prefer voting in-person on Election Day, while Democrats are far more likely to vote by mail; the timeline for when states and their counties process ballots of different types can lead to major gains for each party as they're added to the statewide tallies.

Now, the good news is that we aren't holding the 2024 election in the midst of a global pandemic, and many states have adjusted their electoral rules in recent years to better handle the greater preference for voters to use mail ballots to cast their votes. For instance, Georgia counties must now report their early in-person and mail-in votes within an hour of polls closing, which may lead a large majority of the state's votes to come in pretty quickly and reduce the chances of dramatic partisan shifts as Election Day votes are tallied. Meanwhile, Michigan is allowing localities to pre-process mail ballots ahead of Election Day such that the state will quickly have counts for those types of votes to add in with Election Day votes, again potentially diminishing red or blue shifts. Plus, evidence from early and mail voting suggests we may not see as large a partisan split in preference for voting method, further reducing potential partisan shifts in the election night count.

That being said, some states like Pennsylvania and Wisconsin have not dramatically altered their rules for processing mail ballots, which could mean we once again see some shifts in those places based on the types of ballots that have been tallied. So we still have to be careful to monitor not just where freshly-tallied votes are coming from, but also how they were cast.

The presidential race in Nevada is almost dead even in 538's polling average of the state. While the state went heavily for President Barack Obama in 2008 and 2012 and has remained in Democrats' column since then, it's also inched steadily to the right.

Politics in Nevada are dominated by the Las Vegas metropolitan area, where three-fourths of the Silver State's population lives. And the state's Latino population made up 15% of the electorate in 2020, which means that courting Latino voters in the Las Vegas area has been an important strategy for both parties. And, as we see in polls across the country, Republicans seem to be making gains with these voters: In an average of recent polls, Nevada Latino voters said they would vote for Harris over Trump by a 21-point margin, which would represent a slight drop from the 26-point margin Biden had over Trump among the demographic in 2020.

As for what issues may be particularly important here, the state's service- and hospitality-dominated economy was hit heavily by the COVID-19 pandemic and lockdowns, and the economy remains a top issue for voters there. But a related issue, housing affordability, is also important to voters in the state. While Trump has an advantage in voters' trust on the economy nationwide, Harris may have an advantage on housing in Nevada: According to a September Morning Consult/Bloombergsurvey, voters in the state trust Harris over Trump on the issue of housing by a 10-point margin (49% to 39% of registered voters).