Voting to elect the next president of the United States has started on the east coast of America, with the latest opinion polls indicating that Democrat nominee Hillary Clinton is poised to score a historic victory over Republican rival, Donald Trump.

If she is elected, Ms Clinton would become the 45^th president and the first woman to hold the office.

Opinion polls published on Tuesday showed Ms Clinton widening her advantage in the national vote to more than three percentage points.

When the results of the ten leading national polls published on Tuesday are averaged out, Ms Clinton was sitting on 45.3 per cent to Mr Trump’s 42 per cent.

The lead now enjoyed by Ms Clinton is significant because it is greater than the historical margin of error for US presidential opinion polls (plus or minus 2 per cent).

While Ms Clinton is a clear favourite, most US political commentators are not prepared to write off Mr Trump’s prospects because around 7 per cent of likely voters say they are still undecided.

There is also a chance that Mr Trump could lure traditional Republican voters who have indicated they will support the Libertarian Party candidate, Gary Johnson.

Senior members of Mr Trump’s campaign team were encouraged by a string of late opinion polls for the classic swing state of Florida, which showed him overtaking Ms Clinton.

When each of the Florida polls is averaged out, Mr Trump has a razor thin lead of 0.2 per cent.

A record 45 million Americans have already completed postal and early ballots, which most election experts believe should improve Ms Clinton’s chances.

The states that matter

In Florida, the number of Hispanic voters lodging early votes has more than doubled, an indication that Donald Trump’s anti-immigration policies may have triggered a backlash from Cuban and Mexican communities in Miami.

However, the number of registered Democrats voting early in Florida was dwarfed by the number of voters who identified as Republican.

Hillary Clinton’s poll results are beyond the historic margin of error for US elections.

Mr Trump is clearly in the running to claim Florida, a state he must win if he is to take the presidency.

But his road to the White House is a tough one. Trump is banking on blue-collar voters in America’s industrial rustbelt to secure the 270 delegates he needs to become president.

Mr Trump is almost certain to carry the bellwether manufacturing state of Ohio – a state carried by President Barack Obama in 2012 – but is struggling to eke electoral gains elsewhere in the American Midwest.

Mrs Clinton’s support is holding up in a slew of traditional Democratic strongholds – Minnesota, Wisconsin and Michigan – that were each targeted in Trump campaign advertising.

Mr Trump is threatening to take delegate-rich Pennsylvania, but even a survey of voting intentions commissioned by the Republican Party indicated that Mrs Clinton was likely to get over the line.

According to several US newspaper reports Mr Trump’s advisers have privately conceded that the Republican nominee is not likely to win the swing state of Colorado, which was won by Mr Obama at the past two presidential elections.

Election results are expected to begin to trickle through from east coast states around 1pm on Wednesday, Australian time.

The outcomes of many central and western states such as Colorado and Nevada will not be known until much later in the afternoon.