US Presidential debates provide the crucial opportunity for candidates to make a quot;big differencequot; and influence voters but the history of debating is also littered with gaffes from Richard Nixon’s legendary quot;sweaty upper lipquot; to George H W Bush checking his watch.

With Hillary Clinton and Donald Trump gearing up for their final debate on Wednesday at the University of Nevada in Las Vegas Dean of the Austin Marxe School of Public and International Affairs at Baruch College David Birdsell said the final debate is the quot;last known opportunityquot; to make a big difference but the candidates can also quot;injure themselves through a gaffe a serious misstep of some sortquot;.

quot;This is indeed the last scheduled opportunity for either candidate to make a big differencequot; Birdsell said at a session organised by the New York Foreign Press Centre this week on what to expect in the final debate.

He said as the debates progress the number of people who call themselves undecided shrinks as more and more people make up their mind about which candidate they want to vote for.

While the presidential debates provide the candidates a unique opportunity to win voters with their performance and policy visions Birdsell said the history of presidential debating is littered with gaffes including Nixon’s famous sweaty upper lip and shifting eyes in the first ever presidential debate in 1960 and President Barack Obama’s lackluster performance in his first debate with Mitt Romney in 2012.

The first presidential debate was held in September 1960 between US Senator John F Kennedy the Democratic nominee and Vice President Nixon the Republican nominee in Chicago.

It was also the nation’s first televised debate and Nixon was even criticised for wearing his light-coloured suit against a light-coloured background.

The picture of Nixon dabbing the sweat off his upper lip during the debate is part of legendary debate yore.

Birdsell said there was widespread consensus that Obama too quot;did not do such a great jobquot; in the first debate against Romney in 2012.

quot;Romney looked energetic. He was smart. He had his numbers behind him. And Obama looked a little ‘I’m here I’m going to make my arguments but I’m a little tired and I really wish I weren’t here’quot; Birdsell said.

Obama however was back in the game in the second debate meeting quot;expectations as a tremendously articulate successful communicatorquot; and emerging the victor in the debate.

Birdsell also cited the example of the 1992 town hall debate between former President Bill Clinton who was running for his first term at the presidency and the elder Bush for whom the debate did not go well.

Bush was asked a question by a young woman in the audience on how does he in the White House get affected by the national debate.

Bush had replied quot;I don t understand your question. Let me see if we can get this.quot;nbsp;nbsp;

Bush then went back and forth with the woman for about five minutes saying he does not understand what she was saying to him.

When the moderator explained that the woman was asking about the overall performance of the economy Bush said quot;Oh the economy well the economy affects me every day. How could it not? I am the president.quot;nbsp;nbsp;

Bush then went on to check his watch which Birdsell described as quot;a disastrous response.quot;nbsp;

Birdsell credited Clinton for coming up with the best response in the situation.

Clinton immediately jumped off of his stool and walked to the edge of the stage saying to the woman Tell me again how did that hurt you? What happened to your friends? Well that happens to me as the governor of a small state all the time. Let me tell you what goes on in Arkansas.

Birdsell said Clinton’s response and how he approached the situation quot;created a very tight and effective bond and…may have been the most significant exchange of the entire campaign season.quot;nbsp;

Birdsell however noted that gaffes too can be quot;very very important.quot;nbsp;

quot;And the reason is that they re very easy to synopsise.

It’s hard to synopsise to run a 15-second clip of your brilliance because your brilliance probably didn’t fit into 15 seconds. It probably took 30 90 a longer chunk of time that is not going to hit the evening news.

quot;The gaffe can take seven seconds and run over and over and over and over again and all the evidence shows us that people remember as much or more from the coverage than they do from the debate itself even if they watched it. So that coverage is absolutely dispositive in the way that the debate is perceived post factoquot; he said.

The year 1988 was the last year in which US presidential debates were managed by a press panel typically a print journalist and a couple of broadcast journalists who would ask questions serially of the presidential candidates.

Birdsell said there was a lot of criticism of that format because it gave so much incentive for the journalists to ask really interesting questions like Bernard Shaw’s question to Democratic candidate Michael Dukakis in 1988: quot;Governor if your wife Kitty were raped and murdered would you favour the death penalty for her killer?quot;nbsp;

From 1992 the format changed and included an opening debate with the debaters behind a podium the second debate in the form of a town hall and a third debate which has the same format as the first one.

US Presidential debates have used essentially the same set of formats since 1992.