It used to be the case that the national conventions were the centerpiece of election year. The national conventions were the moment when the parties decided who their presidential and vice presidential candidates would be. That was a moment when great debates took place about the issues of the day. They were political theater of the most dramatic kind. But things started to change in the age of television. In the age of television, party leaders saw conventions in a different way. They saw that the conventions provided a wonderful opportunity to sell their message to American voters as a whole. To begin with, the television networks provided gavel to gavel coverage of everything that took place at the conventions. As a result, the conventions offered an unprecedented opportunity to sell the message for a party. Disagreement, dispute, division, all of that had been a natural part of national conventions up until this time. In the age of television, party leaders were eager to find ways to control the message, to stage-manage conventions more effectively. At the same time, conventions lost their defining mission to decide the ticket. That's because the decision-making moment moved to caucuses and primaries. In most years the caucuses and primaries were decisive enough that the parties had selected their candidate long before convention time. The last convention when there was any doubt about who the party choice would be took place in 1976, when Ronald Reagan came very close to beating President Gerald Ford for the Republican presidential nomination. So these days the conventions are still a key event of election year. Still political theater, but now it's political theater of a very different kind from how it was before, a very heavily stage-managed kind. And now there's a different centerpiece for the campaign. This is the series of presidential debates that take place between the candidates, on television, during the autumn campaign. Presidential debates have become a crucial moment in the making of the American president. And yet, this is a relevantly recent institution, dating back just to 1960 and the campaign between Richard Nixon and John F Kennedy. Back in 1960 there was a hope that the debates would revitalize democratic discourse, that the debates would recapture a lost era of high-minded exchange between serious politicians. In 1960, Americans looked back to the Lincoln-Douglas debates of 1858, seen as a model for a new kind of presidential campaign in the age of television. And sure enough, in 1960, when those debates took place between Kennedy and Nixon, the two candidates engaged in earnest discussion about the issues of the day. But what people tended to remember of those debates involved style, not substance, image, not the issues. And that's particularly true because of the way in which people remember the first debate between Kennedy and Nixon. When Kennedy and Nixon met for that debate, Nixon was unwell. He'd just spent time in hospital because of a leg injury and he looks unwell, he looked gray, he looked tired. JFK, by contrast, looked energetic, he looked presidential. And the story goes that the people who heard the debate on the radio believed that Nixon was the winner in the exchange. But those who saw the debate on television thought that Kennedy had the upper hand. Whether that made any difference to the outcome of the election is another matter. But this effort to inject substance into the presidential campaign perhaps ended up as something that underlined the significance of image instead. Certainly the presidential debates of 1960 provided some key moments of that contest between Kennedy and Nixon. But this wasn't enough to persuade subsequent presidential candidates that the debates were a good idea. In fact, the idea of debates worried candidates, because the very essence of such a political encounter involves the unexpected. And candidates like to control their message, they like to control what goes on in the campaign as much as possible. For them, the right format for the television age was not the television debate, but a television ad, the format that they could control, not the format that was difficult to control. And it was particularly true that the presidential incumbent, the person in the White House, didn't like the idea of a television debate. Presidents believed they had a lot to lose, not much to gain by sharing a platform with their challenger. All this meant that it took time for the TV debates to become a permanent part of the campaign landscape. After those first debates between Kennedy and Nixon in 1960, debates didn't happen again on television until 1976. And it's since then that debates have taken place every four years, becoming, over time, a centerpiece of the campaign for the White House. Just as happened in 1960, these debates usually generate some of the most memorable moments of a campaign. Here are just a few examples. In 1976, the first debate since 1960, Gerald Ford made comments that opponents interpreted as revealing that he misunderstood a key fact about the Cold War, that he wasn't very good as a foreign policy president. Comments that suggested he didn't understand that Eastern Europe was subject to the domination of the Soviet Union in the Cold War. He said that Poland is no longer under Communist domination, under the Ford administration. In 1984, there was a lot of debate about Reagan's age in the campaign between him and his challenger, Walter Mondale. And during the television debate, he took on the charge that he was too old to be President at the age of 73. He said: 'I will not make age an issue of this campaign. I'm not going to exploit, for political purposes, my opponent's youth and inexperience.' Four years later, in 1988, age and inexperience had again become an issue in the campaign, especially involving the Republican candidate for vice president, Dan Quayle. In 1988, Quayle's opponents said that he wasn't up to the job of vice president. Quayle defended himself by saying that he had as much congressional experience as John F Kennedy had done in 1960 when he ran for the White House. In the television debate, his opponent, Senator Lloyd Bentsen said, 'Senator, I served with Jack Kennedy, I knew Jack Kennedy, Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy.' So these debates provide an important focus for the campaign. They usually generate some of the most memorable moments of a presidential campaign. But probably they don't usually make a difference. There's little evidence that debates have a decisive impact on public opinion on the whole. Even so, in a political world where so much is planned as carefully as possible, it's never possible to predict exactly what will happen when presidential candidates meet, in order to engage in debate on television.