But Trump, who has been closing the gap with Clinton in recent weeks in the polls, has everything to win by playing it safe when the pair go face to face for the first time in the campaign.
According to Chief Executive Officer at the United States Studies Centre at the University of Sydney Professor Simon Jackman a non-controversial Trump will be a nightmare for Clinton.
He said Trump who was making significant inroads in key states such as Ohio and Florida, could well end up clinching victory in the debate simply by not being his usual self.
"His best bet would be to be boring, but he may not be able to help himself," Prof Jackman said.
"He may not be able to limit his ability to censor himself."
The Republican nominee has gained significant inroads in the polls in recent weeks, with other party members and advisers urging him to tone down the divisive rhetoric.
Prof Jackman said Clinton was under enormous pressure to close Trump's gain and coming out on top in this debate was a vital "circuit breaker".
He said polls already showed Ohio, which had been won by every president since 1960, was favouring Trump, who needed to win the state if he had any chance of victory.
"This is a lot closer than many people may realise," Prof Jackman said.
"Florida is very close and if this is happening in Ohio, which the Democrats have invested a lot of time and money in, I can't help but wonder what's happening in other states."
Both states are crucial to a Trump victory due to the large number of electoral college votes, however Clinton could still secure victory without them.
"This is why this debate is so important to Clinton, she needs to stop the slow leeching of support away from her," Prof Jackman said.
"There's much more at stake for her strategically because she needs to stop it and soon.
"It will be clash of the titans stuff.
"The big danger will be the less personal and hysterical he is, then the bigger chance there is that he may win."
The first of three debates, today's is considered to be the most vital with around 60 million expected to tune in.
Clinton will be looking to prove Trump is quick to anger, sexist and unfit for the role of Commander in Chief.
Trump will be looking to prove Clinton can't be trusted and is part of everything that's wrong with 'broken America'.
WHAT WILL BE DISCUSSED
The debate is largely seen as a chance for the candidates to prove their worth in two main areas: the economy and national security/foreign policy.
However given both candidates have big personalities, Prof Jackman expects things to turn personal very quickly.
rof Jackman predicts Trump will use the Clinton email scandal to prove she can't be trusted on issues of national security.
As a former secretary of state, Clinton will be looking to promote her strength in the area of foreign policy, but this could prove to be her weakness, he said.
Her biggest hope was that Trump will say something outrageous and divisive so she can divert attention onto his faults.
BATTLE TACTICS
Clinton will be playing it safe and to attack wherever and whenever she can.
Democrats argue Clinton can't out-improvise one of the most unpredictable politicians of the modern era.
Steve Schale, a Democratic strategist who ran Obama's Florida operation in 2008 and advised him four years later, told The Associated Press Clinton will be looking to "grind Trump down".
"We're going through the rollercoaster rides of campaigns. All she can do is just keep ploughing ahead," he said.
Democrat spokesman Brian Fallon said it was crucial Clinton conveyed the "contrast and choice to voters that are tuning in for the first time."
In recent weeks, Trump has become more traditional by reading off teleprompters, rolling out policy proposals and making pitches to minorities.
However this change has left some Democrats uncertain as to how he will act on the day.
Mo Elleithee, a former Clinton aide who's now head of the Georgetown University Institute of Politics and Public Service said the goal was for Clinton to control what she does, not Trump.
"In an unpredictable race against an unpredictable candidate, by definition the only thing you can control is what you do," he said.
"They're focusing on that."
Clinton said she's ready for whatever Trump throws her way.
"I am going to do my very best to communicate as clearly and fearlessly as I can in the face of the insults and the attacks and the bullying and bigotry that we've seen coming from my opponent," she told The Steve Harvey Morning Show.
"I understand it's a contact sport."
CRUCIAL VICTORY
While a Trump victory seemed unfathomable even months ago, the reality is he could win the race to the White House.
This weekend, a professor who has predicted every presidential victory for the past 30 years warned Clinton will lose come November 8.
Allan Lichtman, a distinguished professor of history at American University, told The Washington Post, why he believed Trump is the favourite to win.
By using a system of true/false statements, called the Keys to the White House, Prof Lichtman said his system had predicted eight US president wins since 1984 based on issues such as scandal, social unrest and foreign/military success.
He said if six or more of these statements are found to be false they go against the party in power and they would therefore lose.
Even President Barack Obama, who long dismissed the idea of a future Trump administration has warned Democratic supporters to expect a tight race that Clinton could possibly lose.
Recent polls indicate Trump may have an edge in Iowa and Ohio and is likely in a close race with Clinton in Florida and North Carolina.
"This guy is not qualified to be president," Obama told donors at a Manhattan fundraiser on Sunday. "This should not be a close election, but it will be."
