WASHINGTON — As results begin to come in Tuesday night, here's an hour-by-hour look at what to watch for:
7 p.m. ET
Polls close in Georgia, Indiana, Kentucky, South Carolina, Vermont and Virginia (60 electoral votes) and in much of the state of Florida, a crucial battleground state with 29 electoral votes, but the entire state is not finished until all polls close at 8 p.m. ET.
Georgia is a key state to watch in this grouping, with 16 electoral votes, and NBC News's political unit has it rated it as a toss up. The last Democratic presidential candidate who won Georgia was Bill Clinton in 1992.
Also on the line in Georgia are two Senate seats: Republican Sen. David Perdue is facing challenger Jon Ossoff, and the special election for former Sen. Johnny Isakson's seat includes the appointed incumbent, Sen. Kelly Loeffler as well as GOP Rep. Doug Collins and the leading Democratic candidate Rev. Raphael Warnock. Both these races are toss ups, according to Cook Political Report. But in both races, a candidate needs to get 50 percent of the vote or the race will go to a runoff election.
And two Georgia House races, in the 6th District and 7th District around Atlanta, could give an early look into how fast-changing suburban districts might vote in 2020.
Trump won Florida in 2016 by just under two points, and a Republican hasn't won the presidency without winning Florida since 1924. Unlike some other states, though, it's likely that Florida will have election results relatively early because the state is known for quick tabulating and counts early votes before Election Day.
When South Carolina polls close, all eyes will be on GOP Sen. Lindsey Graham, who is facing Democratic nominee Jaime Harrison in this surprisingly close race. Harrison raised more than $100 million this cycle and the Cook Political Report has this race rated as a toss up.
Virginia looks to be solidly in Joe Biden's reach but one House race in the state could predict how Republicans are doing down the ballot. The state's 5th District is one place where Democrats could expand their House majority and might be a major clue for Republicans early in the night.
7:30 p.m. ET
Polls close in North Carolina, Ohio and West Virginia (38 electoral votes), with North Carolina and Ohio both remaining competitive this cycle. North Carolina, which holds 15 electoral votes, has only voted for a Democratic presidential nominee twice in the last 13 election cycles: Jimmy Carter in 1976 and Barack Obama in 2008.
President Trump carried the state by just about three points in 2016.
North Carolina's Senate race pits incumbent GOP Sen. Thom Tillis against former Democratic state senator and Army veteran Cal Cunningham and could be a key race in determining which party will control the Senate for the next two years.
Ohio has a pattern of predicting the presidential winner — the state has voted for the eventual winner of every presidential contest since 1944 with just one exception: Picking Richard Nixon over John F. Kennedy in 1960. No Republican president has ever won the presidency without Ohio. But while the state has historically picked the winner, that bellwether could be coming to an end due to demographic shifts in the state.
8 p.m. ET
While New Hampshire was a reliably Republican state through the 1980s, presidential elections there have been closer more recently. Six of the last seven elections have ultimately broken for Democrats, and NBC News's political unit has it ranked as lean Democratic. The last time a Republican presidential nominee won the state was 2000.
Pennsylvania carries 20 electoral votes, and the state has seen major political shifts recently. Joe Biden's state of birth voted for President Obama in 2008 and 2012, but then swung to President Trump in 2016.
But it could be a while before we know the state's results because early votes cannot start being counted until Election Day.
8:30 p.m. ET
Just one state, Arkansas, closes at 8:30 p.m. and will award six electoral votes.
9 p.m. ET
Polls close in fourteen states with a total of 156 electoral votes on the line.
Arizona is one of this election's biggest battlegrounds for both the presidency and the Senate. While the state was once reliably Republican, NBC News' political unit has rated it as a toss up this cycle. The last time a Democratic nominee carried the state was in 1996 but Trump won it by just over three points in 2016.
Arizona GOP Sen. Martha McSally is facing a tough race for her seat against Democratic challenger Mark Kelly. The Cook Political Report has rated that race as lean Democratic.
Michigan is rated as a lean Democratic state for the presidential contest but Trump won it by fewer than 11,000 votes in 2016 — the first time the Democratic Party lost the state in over 25 years. Democratic Sen. Gary Peters is also facing a challenge from Republican John James, a veteran. While polling has shown Peters with a consistent lead, the race has remained close.
Texas, a state that boasts 38 electoral votes, hasn't elected a Democrat to statewide office in more than 25 years, and hasn't voted for a Democratic presidential nominee since 1976. But this year, NBC News' political unit has rated Texas as a toss up — Trump won the state by 9 points in 2016.
While Texas Sen. John Cornyn isn't facing the same challenge that Sen. Ted Cruz faced in 2018, Democratic challenger M.J. Hegar has continued to be well-funded throughout the campaign.
Wisconsin, a state once considered part of Democrats' "blue wall", voted for Trump by less than 23,000 votes in 2016. Obama carried the state in 2008 and 2012, and Biden is hoping to recapture it. The NBC News political unit has ranked the state as lean Democratic.
10 p.m. ET
Iowa's six electoral votes are up for grabs this cycle after voting for Trump in 2016. Obama carried the state decisively in 2008 and 2012. And the state sided with Democrats in six out of seven elections between 1988 and 2012. The NBC News political unit has rated the presidential contest as a toss up.
Republican Iowa Sen. Joni Ernst is defending her seat against Democrat Theresa Greenfield who's made inroads in the final weeks of the campaign, and this may be one of the most competitive Senate contests of the night.
In Nevada, two-thirds of the vote usually come from Democratic Clark County — the area surrounding Las Vegas. The state went for Hillary Clinton in 2016 and since 1908, Nevada has only sided with the losing presidential candidate twice: In 1976 when voters picked Gerald Ford, and in 2016.
11 p.m. ET
12 a.m. ET
Hawaii will close its polls at 12 a.m., and will contribute four total electoral votes.
1 a.m. ET
The final state to close its polls is Alaska at 1 a.m. Alaska holds three electoral votes.