[WASHINGTON] Democrat Hillary Clinton and Republican Donald Trump face off for the first time on Monday in a high stakes presidential debate that could shift the course of the neck-and-neck 2016 campaign for the White House.
The highly anticipated clash between the Democratic former secretary of state and Republican real estate tycoon has generated wide interest nationally and internationally six weeks before the Nov 8 election.
Opinion polls show the two candidates in a very tight race, with the latest Reuters/Ipsos polling showing Clinton ahead by 4 percentage points, with 41 percent of likely voters.
The 90-minute debate, set to start at 9pm EDT (0100 GMT on Tuesday), could sway undecided and independent voters who have yet to make up their minds as well as voters from both parties who have tuned out the election until now.
A second Reuters/Ipsos poll released on Monday showed half of America's likely voters would rely on the debates to help them make their choice. More than half, 61 per cent, were hoping for a civil debate and were not interested in the bitterness shown on the campaign trail.
The size of the television-viewing audience is expected to challenge the record of 80 million Americans who watched 1980's encounter between Democratic President Jimmy Carter and Republican Ronald Reagan. Some commentators forecast Super Bowl-sized viewership of about 100 million people.
By contrast with the single-party debates held during the Republican and Democratic state nominating contests, the audience will be asked to remain silent and not applaud or respond to the candidates' remarks. The debate will be divided into six 15-minute segments.
Mrs Clinton won a coin toss and chose to take the first question. She will have two minutes to answer, after which Mr Trump will be given equal time. Mr Trump will then be given the first question at the beginning of the next segment.
The debate, at Hofstra University on New York state's Long Island, is the first of three planned presidential debates and one vice presidential debate.
With the contest tightening, Wall Street investors grew more jittery on Monday, contributing to a fall in stocks. Some investors see the close race sparking volatility in sectors that include health insurers, drugmakers and industrials.
In Asia on Tuesday, uncertainty gripped markets as investors braced for the potentially consequential debate by shunning stocks while favoring safe haven bonds and the yen.
Markets have tended to see Mrs Clinton as the candidate of the status quo, while few are sure what a Trump presidency might mean for US foreign policy, trade and the domestic economy.
Both Mr Trump and Mrs Clinton, shown in opinion polls to be the least liked White House candidates in modern history, hope to use the debate to erase lingering voter doubts and address campaign-trail weaknesses.
The volatile Mr Trump, a former reality television star, will have an opportunity to show a depth and steadiness worthy of a commander in chief, while the cautious Mrs Clinton, a former US senator and first lady, will have a chance to connect directly with voters who view her as too secretive, strategists said.
Mr Trump, a political newcomer who has at times shown more affinity for put-downs than policy, could benefit from lower voter expectations.
"There is no question it's a lower bar for Trump," said Dan Schnur, a former Republican strategist and now a political scientist at the University of Southern California.
"He doesn't have to be brilliant, he just can't be too bombastic."
The stakes are enormous. Mrs Clinton once had a sizable lead, but that has evaporated amid more questions about her family's foundation and use of a private email server while secretary of state under President Barack Obama.
If the election were held today, Mrs Clinton would still defeat Mr Trump, with an 88 per cent chance of reaching the 270 electoral college votes needed, according to the Reuters/Ipsos States of the Nation project, which is based on a weekly online tracking poll of more than 15,000 Americans.
Two other presidential candidates - Libertarian Gary Johnson and Green Party candidate Jill Stein - were not invited to take part in the debate because neither had obtained at least 15 per cent support in national polls, the threshold established to qualify.
Mrs Clinton, 68, and Mr Trump, 70, have regularly exchanged sharp insults at a distance, raising the prospect of a fiery grudge match. Mr Trump refers to Mrs Clinton as "Crooked Hillary" and has called for her jailing for the email controversy. Mrs Clinton denounces Mr Trump as temperamentally unfit for the White House.
Mr Trump dominated the crowded Republican debates with rapid-fire attacks on his rivals but has no experience in a one-on-one debate setting that requires more prolonged discussion of issues.
Mrs Clinton has participated in many one-on-one debates on the national stage: with Mr Obama during her unsuccessful 2008 presidential campaign and with US Senator Bernie Sanders in the Democratic nominating race earlier this year.
Mrs Clinton's camp has done its best to raise the bar for Mr Trump, and in television interviews on Monday both campaigns tried to frame expectations.
"What we don't want to have is some sort of double standard where Donald Trump can get the most-improved award, but Hillary Clinton ... is getting judged on the fine points of policy," Mrs Clinton campaign manager Robby Mook told NBC News, calling Trump "an entertainer".
Mr Trump's campaign manager, Kellyanne Conway, said Mrs Clinton's vast experience was unlikely to translate onto the debate stage, where Mr Trump held an advantage.
"He's not going to be robotic and scripted," she said separately on NBC.
The role of moderator Lester Holt of NBC News also came under scrutiny before the debate, with the Clinton campaign and her Democratic supporters urging him to correct Mr Trump if he makes false claims.
Mr Trump also has tried to influence Mr Holt and moderators of the other showdowns with Mrs Clinton, saying the candidates should be the ones to correct the record.