After months of campaigning, hours of election speeches and debates, and hundreds of opinion polls tracking the ebb and flow of the 2008 US presidential election, the time of reckoning is near.
Keep this guide to US election night to hand to check what will be happening when and what to look out for.
Remember each state has a certain number of electors in the electoral college that elects the president, so the winner is the one who wins enough states to stack up 270 electors' votes.
We give the times the polls close in various states (some straddle more than one time zone) but if there is heavy turnout and/or problems with the voting equipment, some precincts may stay open longer.
KEY BATTLEGROUND STATES
Too close to call: Colorado, Virginia, North Carolina, Indiana, Montana, Missouri, North Dakota, Georgia, Arizona
Swing states now and in 2004: Michigan, Pennsylvania, Ohio, Florida
In some cases, projected results will emerge immediately after voting ends but in other cases, depending on how tight the race is, they may not emerge for several hours (or in the case of 2000, several weeks).
So here goes:
2300 GMT (1800 EST): The first polls close, but election night really gets going in another hour.
2400 GMT (1900 EST): Polls close in Georgia, Kentucky, South Carolina, Vermont but the ones to watch are Indiana and Virginia. Both have gone Republican since 1964, so if either of them go for Barack Obama, it could spell a miserable night for John McCain.
But if Senator McCain secures both, he is still in with a chance.
0030 GMT (1930 EST): Get set for drama here. Polls close in the key battleground state of Ohio - it is finely balanced and we might have a long wait before we know which way it has gone. In 2004, the result was not called for several hours.
North Carolina has been fiercely targeted by the Obama campaign, which has flooded the state with money and volunteers.
Democratic success here could suggest Senator Obama is on a roll but a McCain triumph will signal late movement towards the Republican.
West Virginia should be called on the hour - a Republican win.
0100 GMT (2000 EST): The night really speeds up now. Polls close in 15 states and the District of Columbia. Which way most of them will go seems pretty clear and the results should come quickly. But watch out for these:
• Missouri - the classic bellwether state. It has backed the winner in every presidential race since 1904, except President Eisenhower in 1956, and the polls suggest a very tight contest.
• Florida -its 27 electoral college votes have been bitterly fought over - it's that important and a state Mr McCain simply must win.
• Pennsylvania -it has voted Democratic in the last five elections but has become another of the key battlegrounds. Mr McCain really has to capture this Democratic "blue" state - the view is if he cannot win here, he almost certainly will not win the election.
• New Hampshire - Mr McCain is hoping to win here and he is in with a chance. The state only has four electoral college votes but if the race is tight, they could be crucial.
Also closing here are Mr Obama's home state of Illinois and Delaware - home state of his running mate Joe Biden.
(Note for election buffs: Maine - and Nebraska which closes in an hour - can split their electoral college vote count - the rest use the winner-takes-all method.)
0130 GMT (2030 EST): Polls close in Arkansas and it is safely Republican. So if you need a quick breather, then now is your chance as in 30 minutes things could get really interesting.
0200 GMT (2100 EST): Another big bunch of states closes now and it is the earliest either candidate can realistically reach the magic 270.
So depending on how things stand, it will be all over bar the shouting or the election night just got a lot longer.
Mr Obama has been targeting Colorado and New Mexico - which both went Republican in 2004. He really needs to win these if he hasn't picked up any Republican "red "states by now.
Mr McCain needs to win the blue states of Michigan, Minnesota and Wisconsin if he is losing red states and has not secured Pennsylvania.
Polls also close in Mr McCain's home state of Arizona.
ELECTION DAY ON THE BBC
Live text updates through the day and night, with input from BBC correspondents around the US
Results as they come in, on a live updating map from midnight GMT
Streaming video of the BBC election night programme in Washington
Analysis from BBC North America editor Justin Webb in Washington, and Gavin Hewitt and Matthew Price at the candidates' HQs
0300 GMT (2200 EST): Last of the real battleground states close now. Mr Obama is expected to win in Iowa so if he doesn't that will be a real upset.
Watch out for Nevada - the state has an uncanny knack of backing the eventual winner. The Obama campaign has put a lot of money and workers here, so we will see if that paid off.
Montana until recently was not seen as a possible Democratic win but now it is.
0400 GMT (2300 EST): States closing here should be safe for their respective parties - Idaho (four votes) for Mr McCain, while California, Hawaii, Oregon and Washington are set to give Mr Obama 77 electoral votes.
So if the Democratic candidate has already won states like Virginia, North Carolina, Ohio, Indiana, or Florida, then he has it in the bag.
0600 GMT (0100 EST): All polls have closed in Alaska and it would be a huge surprise if it did not stay Republican, given that the state's governor, Sarah Palin, is on the ticket.
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