The biggest upset in US political history looms with Donald Trump smashing expectations in battleground states to give himself a genuine chance at becoming the next president of the United States.

Despite Hillary Clinton starting the day as an almost unbackable favourite to win the White House, her opponent could now win critical states like Florida, North Carolina and Ohio, giving him a clear path to victory.

While the result remains in the balance, Mr Trump is much closer to victory at this stage of the count than many pollsters and pundits dared to forecast.

Supporters of Hillary Clinton are starting to voice their concerns over an upset outcome.

World markets are roiling at the prospect of the Trump victory. More than $40 billion has been wiped from Australian shares and US futures, which point to the likely performance of US stocks when markets open, are pointing to massive dive.

Electors in three traditional Democratic-leaning states appearing to stoke a rally in support for Mr Trump.

At 2pm AEST, Donald Trump led Hillary Clinton by 36 electoral college votes (140 to 104), according to media reports, with the Republicans also expected to retain control of the US House of Representatives.

There are 538 Electoral College votes allotted to the 50 states and the District of Columbia. It takes 270 votes to win.

With voting completed in more than two-thirds of the 50 US states, the race was too close to call in Ohio, Florida, North Carolina, New Hampshire and Virginia, states that could be vital to deciding which contender wins the presidency

Unsettling progress

Mr Trump’s recovery in the polls has spooked investors, with most US stock market indicators closing at three-month lows on Friday.

The leading weekly investment newspaper Barron’s warned readers at the weekend that US-listed stocks could plummet by as much as ten per cent if Trump wins.

Outspoken documentary film-maker and anti-Trump campaigner, Mike Moore, accused Democratic party strategists of underestimating the electoral appeal of the Republican nominee for most of the campaign.

“I’ve been saying since the summer that Trump can definitely win. Liberals, Hillary supporters, didn’t believe it,” he told CNBC. “People are upset, they are angry at the system.

“And they see Trump – not so much they agree with him but see him as the human molotov cocktail they get to toss into the system like with Brexit and blow it up, send a message.”

Trump eyes traditional Democratic strongholds

Polls published at the weekend show Mr Trump has overtaken Mrs Clinton in the usually Democrat-leaning states of New Hampshire and Nevada.

He has also reduced his Democrat rival’s lead in the delegate-rich state of Pennsylvania to just 2 percentage points, after trailing by an average of 6 per cent throughout October.

On Saturday night, Mrs Clinton held a rally in Philadelphia – Pennsylvania’s biggest city – where she was joined by a slew of celebrities, including pop star, Katy Perry.

For several weeks Mr Trump has been building a healthy lead in the classic bellwether state of Ohio.

Since 1964, every successful presidential candidate has won Ohio.

Winning Pennsylvania and Ohio would give Mr Trump a viable chance of securing the 270 delegates he needs to move in to the White House.

He would also have to take Florida, North Carolina and Colorado, and at least one other battleground state — of which there are around 10 — to get over the line.

While opinion polls taken in the first week of November show Mrs Clinton holding a comfortable lead in the rust-belt state of Michigan, Democrat strategists are worried that blue-collar voters have begun to swing heavily to Mr Trump.

Ms Clinton must win Ohio to keep Mr Trump out of office it seems. Photo: Getty

In a move to shore up support for Clinton in the economically stricken state, President Barack Obama will stage rallies in Detroit and Ann Arbor on Monday.

The Obama administration signed off on an $80 billion auto industry bailout that some academics claim saved more than 1 million manufacturing jobs across the US.

Trump is boosting his support throughout the Midwestern states such as Michigan and Wisconsin by appealing to blue collar voters who are disillusioned with the political status quo in Washington.

Although this demographic has mostly voted for Democratic candidates in the past, Hillary Clinton’s campaign has struggled to connect with these voters.

According to the respected conservative columnist David Brooks of the New York Times, a Clinton victory would likely owe more to educated voters on high incomes.

“Basically, less educated or high school-educated whites are going to Trump,” Brooks told the Public Broadcasting Service. “It doesn’t matter what the guy does – and college-educated going to Clinton. “Sometimes, you get the sense that the campaign barely matters.”

The “positives” for Clinton

Even though Trump is finishing the campaign stronger than Clinton, it is not clear whether he has enough momentum to become the most powerful human on the planet.

Mr Trump could cause an upset. Photo: Getty

There are still a couple of factors working in Clinton’s favour.

First, her national vote is holding up because Trump’s gains in the polls are mostly coming at the expense of the Libertarian Party candidate, Gary Johnson.

Second, Clinton’s prospects appear to have strengthened in Florida – a delegate-rich swing state –because of a bigger than expected turnout by Hispanic electors in early voting.

If the high turnout is replicated at the polls on election day, Trump’s inflammatory rhetoric about Mexican immigrants might end up costing him the election.