Key moments in US presidential debates that changed election campaigns
US presidential debates are widely believed to be potential game-changers in elections.
They play a key part in the election campaign, enabling voters to learn more about candidates and their policies. Debates also have the power to swing voting intentions.
Ahead of the much-anticipated debate between Democratic presidential hopeful Hillary Clinton and her Republican rival Donald Trump, we look back at some key moments in US election history that changed campaigns.
1960: John F Kennedy v Richard Nixon
John F Kennedy's presidential debates with Richard Nixon were the first between candidates of opposing political parties, and also the first to be televised.
The debates were a major turning point in the 1960 election, with a calm and confident performance helping JFK secure the presidency.
Polls revealed that over half of all voters had been influenced by the debates, with 6% saying the debates alone influenced their choice.
1980: Ronald Reagan v Jimmy Carter
In the first of the 1980 debates, incumbent president Jimmy Carter accused Ronald Reagan of planning to cut Medicare.
Reagan responded with the now famous line "There you go again", which became the enduring phrase of the election.
Reagan subsequently beat Carter in a Republican landslide, ushering in the defining "Reagan Era" - a significant realignment of US politics at the time.
1984: Ronald Reagan v Walter Mondale
Accused by Democrat Water Mondale of being past his former glory, Ronald Reagan launched a withering attack against his rival about his youth and inexperience.
Reagan went on to win 49 of the 50 US states in the presidential election, becoming one of only two candidates to do so (the other being Richard Nixon in the 1972 presidential election).
1988: George Bush Snr v Michael Dukakis
Against a backdrop of social unrest in the US and intense focus on law and order issues, Michael Dukakis was asked in a debate if he would ask for the death penalty if his wife was raped and murdered.
The Democrat relied "no" - an answer believed by some political commentators to have lost him momentum in the election.
1992: Bill Clinton v George Bush Snr
George Bush Snr floundered answering a question about the recession and was twice caught looking at his watch.
It is believed Bush's less than stellar performance contributed to Clinton's final push over the edge to election victory.
2012: Barack Obama v Mitt Romney
During one of his debates with Barack Obama, Mitt Romney got his facts mixed up when trying to criticise Obama's response to a 2012 attack on the US diplomatic compound in Benghazi, Libya.
Moderator Candy Crowley picked up on the gaffe, and Obama asked her to repeat herself louder. Romney never really recovered from the blunder, and Obama went on to secure his historic presidential victory in November 2012.