Televised debates are key moments during U.S. presidential election campaigns. While they rarely become game changers, they can capture the public's interest and turn pithy statements or small gaffes into national catchphrases. More than 67 million people tuned in to the first presidential debate between President Barack Obama and Republican challenger Mitt Romney.
Tuesday's second presidential debate will take place at Hofstra University in Hempstead, New York, and it is also expected to be a big draw.
Here is a brief look at the most memorable moments in U.S. debate history. Which is the most memorable? You decide by voting and tweeting for your favourites – good or bad. You can click any link in the text to jump to that part of the clip.