DONALD Trump is to target states seen as Democratic strongholds in the last two days of the US presidential campaign.

The Republican nominee will visit Pennsylvania, Michigan and Minnesota, which has not gone Republican since 1972. He started off a four-state tour on Saturday in Florida, where rival Hillary Clinton also campaigned and unveiled an advert to run in nearly a dozen states, set to the Katy Perry song, Roar.

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Trump is also to spend millions on an advertising campaign aimed at wooing voters with adverts tailored to their psychological profile.

The polls continue to put Clinton ahead of her rival but all are within the margin of error with the swing seats, the real battleground, almost impossible to call.

The Herald: Donald Trump. Bu Chip Somodevilla/Getty ImagesDonald Trump. Bu Chip Somodevilla/Getty Images

Trump’s last-minute media blitz of psychologically tailored ads are being prepared at cost of more than $5m and involve "data-mining" experts collecting thousands of bits of information about prospective voters. They then build up a psychological profile, to adapt political ads to his or her personality and beliefs.

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The personality test dips into the type of people to target and attempts to measure openness, conscientiousness, extroversion, agreeableness and level of neurosis. The data is mined from online and social media surveys about voting, shopping and television viewing history.

Clinton basked in some star power in Cleveland on Friday night at a free concert with singer Beyonce and rapper husband Jay Z.

In response on Friday at a jam-packed rally at Hershey Pennsylvania Trump sought to blow away the stardust: "And I didn't have to bring J-Lo or Jay-Z," he told the crowd.

Pennsylvania is one of the few states that does not allow early voting, so election day turnout is everything. Clinton has a steady lead in the polls but cannot take it for granted.

Read more: Salmond says Trump will display threatening behaviour if he wins Presidency

Today Clinton takes the stage with basketball star LeBron James in Cleveland, a rare dive into politics for a superstar athlete still in the prime of his career. She will return on Monday night to Philadelphia for a joint rally with her husband and Barack and Michelle Obama.

The Herald: Hillary Clinton. AP Photo/Andrew HarnikHillary Clinton. AP Photo/Andrew Harnik

Responding to concerns about an anaemic turnout among young adults and African-Americans – two of the core constituents of the Obama coalition and crucial to Clinton – the Democratic Party has enlisted a slew of pop stars such as Perry, Pharrell Williams, Jay-Z, and for older blue collar Democrats who might be tempted to vote for Trump, stalwarts Bruce Springsteen and Jon Bon Jovi. Concert tickets must be picked up in person, near early voting sites.

On the campaign trail Barack Obama framed the contest in apocalyptic terms: "The fate of the world is teetering and you, North Carolina (a crucial swing state), are going to have to make sure that we push it in the right direction.”

For the past fortnight Trump has been holding two or three rallies a day, in New Hampshire, Florida, Pennsylvania, Colorado, Iowa, Ohio, Nevada, Michigan and Wisconsin, flying between them in his branded Boeing 757.

None of the Republican party’s most respected leaders has campaigned for him. Presidents Bush Senior and Junior are sitting this one out.

Read more: Everything you ever wanted to know about the US Presidential election - but were afraid to ask

Trump has vowed to spend some of the final hours of the presidential campaign in Democratic heartlands in a bid to pull off a shock in states that have not voted for a Republican in decades. He plans to head to Minnesota in the final three days of the campaign.

"We're going into what they used to call Democrat strongholds, where we're now either tied or leading," he told a rowdy crowd at a rally in Tampa yesterday. "We're going to Minnesota, which traditionally has not been Republican at all."

The Herald:

Public polls from earlier this autumn found a comfortable lead for Clinton in Minnesota.

Read more: Salmond says Trump will display threatening behaviour if he wins Presidency

At this stage, the sheer number of polls are bewildering. Nationally, Clinton’s lead seems to have stabilised at around two or three per cent after a week of momentum for Trump based on the FBI letter to Congress that Clinton was again under investigation over emails, although from whom and to whom is still unclear.

In swing state polls, she appears much more vulnerable than a fortnight ago. Trump is level in New Hampshire and within striking distance in Michigan.

State opinion polls suggest Florida, the largest of the swing state, is a nail-biter and Republicans are pointing to suggestions that traditionally Democratic African-American are not turning out as proof they can win. Democrats say Hispanic voters are showing up in droves to vote early while Republicans point to signs that reliably Democratic African-American voters are not coming out in the numbers that helped deliver the state to President Barack Obama.

FiveThirtyEight, the most respected polling analysts - but also the most cautious - rate her chances of winning the presidency at 65 per cent. The Upshot, at the New York Times, has her at 85 per cent. The Huffington Post’s model has her winning chance at 97.9 per cent.

Read more: Everything you ever wanted to know about the US Presidential election - but were afraid to ask

Trump is, remarkably, still in contention despite having been portrayed as an alleged serial sexual predator, a huckster who cheats vulnerable people out of their savings, a welsher who refuses to pay his debts and – proudly and admittedly – someone who pays no taxes.

He has also demonstrated, again and again, that he is ignorant in matters of domestic and foreign policy and uninterested in learning.

Conservative newspapers that have not endorsed a Democrat in a century have lined up behind Clinton, leaving him with the backing of the National Enquirer, the Las Vegas Review-Journal and the Crusader, the unofficial newspaper of the Ku Klux Klan.

Read more: Salmond says Trump will display threatening behaviour if he wins Presidency

Trump often compares his movement to the Leave campaign in Britain, and to some extent it is, in part, a protest vote against rising economic inequality and metropolitan condescension.

“Our magnificent, historic movement has surprised the world and defied expectations at every single turn,” Trump told supporters in Orlando. “And now, next Tuesday, we will have one more glorious surprise for the pundits, the politicians and the special interests.”

Trump’s claim that the polls consistently underestimate his support appears to be unfounded. The biggest surge in registration requests this year has come from young people and minorities – both groups that are more likely to vote for Clinton.

In the weekly Republican Party address, Trump said he would bring badly needed change to government, including plans to create millions of jobs, cut taxes and repeal and replace the healthcare law known as Obamacare. He repeated his promises to fix "terrible trade deals", end illegal immigration and suspend the admission of Syrian refugees.

Read more: Everything you ever wanted to know about the US Presidential election - but were afraid to ask

He also vowed to rebuild the military and "take care of our great, great veterans" and promised to stop jobs disappearing from America and cut taxes for the middle classes.

At the deadline nears and tensions rise fuelled by the increasingly hostile rhetoric, federal judges in Ohio and Nevada have issued injunctions to prevent Trump supporters intimidating voters on Election Day.

It is feared hackers may also try to disrupt internet service or alter registration records to sow confusion and lend credence to claims of a “rigged” election.