The stay-up-all-night guide to the US presidential election

Barack Obama, Mitt Romney, US election

The Week’s hour-by-hour breakdown of what to watch for as the election results come through from the States

LAST UPDATED AT 15:25 ON Tue 6 Nov 2012

FOR those who enjoy the once-every-four-years fix of US political drama, the TV action starts at 11.35pm tonight when both BBC1 and ITV kick off their all-night US presidential election coverage, 25 minutes before the first polling stations close in the States.

The process by which predictions and eventual results are arrived at differs substantially from that with which British voters are familiar. For starters, the map of America shows Democrats as blue and Republicans as red in a reversal of their left-right equivalents in the UK.

Obama and Romney are vying for the 538 Electoral College votes that are distributed among America's 50 states plus the District of Columbia. The winner of the popular vote in each state takes all of that state's Electoral College votes.

Whoever takes an overall majority of the Electoral College votes - 270 or more - becomes the president.

In 2008, Obama took 365 Electoral College votes to John McCain's 173. Given the closeness of the opinion polls, he has no chance of emulating that tonight.

In the US, state results are 'called' for one party or the other during election night by the TV networks - ABC, CBS, NBC, CNN and Fox - and the Associated Press, based on exit poll data compiled by pollsters Edison Research.

In recent years this has led to controversy when states have been 'called' for the wrong party or else the political motives of the network making the 'call' have been questioned, as happened in Florida in 2000.

In an election as close as today's is expected to be, no 'call' is expected from the networks until they’re feeling 99.5 per cent confident they’ve got it right.

This means that the result in closely-fought states might not be known until several hours after the polls close - so be prepared to stay on your sofas through to breakfast without a clear-cut result.

Here’s the order of play – and what to watch for - from midnight (UK time) onwards:

Midnight: The first batch of states close their polls. Georgia, Indiana, Kentucky and South Carolina should all go to Mitt Romney, while Obama is projected to win Vermont.

The key one to watch for here is Virginia. The state went to Obama by six points in 2008, and it really is a must-win for Mitt Romney if he's to have a chance of building a viable majority. An early call here could suggest a big win for either candidate.

12.30am: Polls close in North Carolina, West Virginia and Ohio. Obama scraped home in North Carolina last time, but has little chance of holding on to the 15 Electoral College votes today. If he does it means unpredicted pain for Romney, who will himself be looking for a wide margin of victory if he's to be on course for the White House.

Ohio is the crucial state for both candidates. It has voted for the winner of the presidential poll in every election since 1960. Without it, the maths for Romney verge on the impossible, while Obama would begin to sweat if he saw Ohio turn from blue to red.

1am: Polling closes in the District of Columbia and 16 states including Pennsylvania, Florida and New Hampshire - all three of which went for Obama last time.

The Romney campaign have made a late effort to try to turn Pennsylvania this year, pouring in advertising money and blitzing the state with visits, and a victory here would suddenly make Romney the favourite.

Florida, with its 29 Electoral College votes (the equal third largest prize after California and Texas), was until very recently widely expected to return to the Republicans. However, the arrival of Hurricane Sandy and Romney's uncertain position on federal disaster aid now make this a toss-up. Obama could be home by more than 100 votes if he wins Florida.

1.30am: Arkansas, a solid Romney state, should declare soon after its polls close. It used to vote for its favourite son Bill Clinton, but Obama is almost 30 points behind in polling here.

2am: Fourteen more states wrap up, including Colorado, Michigan and Wisconsin. Colorado suddenly looked to be a possibility last week for Romney, as a string of polls put him tied with or ahead of the president. The state has seen high levels of voter registration benefiting both parties.

The solidly Democratic state of Michigan also showed some signs of warming to Romney - his father George was the Governor here - but Obama’s auto industry bailout and a strong get-out-the-vote operation by the Democrats means it would be a major upset if the President lost this one.

In Wisconsin, Obama romped home by 14 per cent in 2008, and although his lead has been more than halved he seems likely to take the state’s 10 Electoral College votes.

3am: Polls in Iowa, Montana, Nevada and Utah close. Utah is the centre of the Mormon faith in the US, and Mitt Romney could have a majority of more than 50 per cent here - unfortunately for him, the state only has six votes.

Iowa is the sort of Midwestern state that the Republicans should be rolling up. But again, a surge by Romney petered out over the last weeks of the campaign and Obama is now expected to win here.

The state of Nevada should have been rich pickings for Romney, as the home of Las Vegas has been economically crippled over the last four years and seen massive layoffs. But a strong Democrat ground game - Senator Harry Reid held onto his seat in 2010 against a Republican onslaught - and a growing Hispanic population puts Nevada firmly in the blue column.

4am: Five more states call it a day. Most of them - like the 55-vote behemoth, California and Hawaii - should be easy Democrat holds.

6am: By the time Sarah Palin's Alaska, a dead cert for Romney, rounds things off for the evening, the overall winner will hopefully be known. · 

For further concise, balanced comment and analysis on the week's news, try The Week magazine. Subscribe today and get 6 issues completely free.