US ELECTION LIVE UPDATES: Barack Obama re-elected US president

The polls have opened in most American states in what looks to be the closest presidential race in history. NewstalkZB.co.nz brings you LIVE UPDATES and a live blog of the day's developments as millions of Americans decide to elect either Democrat Barack Obama or Republican Mitt Romney as president. We'll keep you up to date as the campaign comes to a close and the votes start being counted.

We'll also have LIVE coverage throughout the day from our newsroom and correspondents on-air and on our online live stream, including Political Editor Barry Soper live from Chicago.

First results are expected around 4pm NZT this afternoon.

To win the presidency, a candidate needs to win 270 electoral college votes and each state has a different amount of votes to allocate to candidates.

There are a number of states where polling would suggest a candidate has that state's votes in the bag, but there are about 10 battleground states where polling suggests it could go either way.

One of these states is Ohio which is seen as a key to winning the presidency - no presidential candidate has won in the past 50 years without taking Ohio.

Other swing states are Colorado, Florida, Michigan, Nevada, New Hampshire, North Carolina, Pennsylvania, Virginia and Wisconsin.

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