The US voting system explained
Chris Hammer outlines how the electoral college system is used to elect an American president.PT0M0S 620 349
HERE is an hour-by-hour viewer's guide to election night 2012, showing you which results to watch to get an early glimpse of national trends:
■ 6pm US Eastern (10am Australian Eastern): Kentucky (most) and Indiana (most)
Romney should win these easily, but the TV networks won't project a victor until all polls close at 7pm US time. A Romney blowout in Indiana is bad for Obama.
The Indiana Senate race is vital to Republican chances of capturing the Senate. If Richard Mourdock squanders his early lead, it would complicate Republicans' chances of gaining the four seats to ensure Senate control.
■ 7pm US Eastern: Virginia, Florida (most)
If Romney loses these states, it's almost impossible for him to reach 270 electoral votes. If Obama is trailing, it could be a late night in front of the TV for Americans.
■ 7.30pm US Eastern: Ohio, North Carolina
If Romney doesn't win Ohio, where he's been trailing in almost every pre-election poll, it could be a long night for the challenger. Obama has been stubbornly competitive in North Carolina, a must-win state for Romney. If the networks quickly project a Romney triumph in North Carolina, that's a positive sign for Republicans.
■8pm US Eastern: New Hampshire (final), Pennsylvania, Connecticut, Missouri, Texas (most)
The ones to watch are New Hampshire and Pennsylvania. Romney invested heavily in Pennsylvania last week in an attempt to pull an upset, and has scheduled an election day stop there. If he is hanging tight or winning there, it's good news for Republicans.
An Obama win in New Hampshire could be a sign of things to come in other swing states such as Iowa and Nevada.
■9pm US Eastern: Wisconsin, Michigan, Minnesota, Colorado, Arizona
If Romney has already lost in either Ohio or Virginia, he'll need an upset win in Michigan, Wisconsin or Minnesota.
In Colorado, an estimated 80 per cent of voters have already cast early ballots. Republicans expect to win here, so an Obama lead would be devastating for the challenger.
■10pm US Eastern (2pm Australian Eastern): Iowa and Nevada
If Romney wins both, it's a sign of a tight finish. If Obama sweeps, it increases the pressure on Romney.