'I've seen how one slip of the tongue can be fatal'

Britain's political leaders should probably heed the advice of Jim Lehrer, the veteran American broadcaster who has moderated 10 presidential contests. Not that Lehrer's words will give Gordon Brown, David Cameron or Nick Clegg any comfort. Lehrer, a veteran at America's Public Broadcasting Service, believes a single slip could be fatal. "It certainly is a possibility. Somebody could say something that would just throw away the election," he told the Observer . American politics is littered with examples of debating mistakes that helped to derail bids to win the White House. In 1988, the Democratic candidate, Michael Dukakis, was hugely damaged after sticking by his anti-death penalty views when he was asked how he would react to the rape and murder of his wife. Gerald Ford, while debating Jimmy Carter in 1976, claimed to audible gasps: "Poland is no longer under communist domination." Like Dukakis, he went on to lose the election. The pressure on candidates is immense, but Lehrer thinks British leaders will be under even greater strain than their American counterparts. US campaigns go on for months, with a long primary process under which a slate of candidates is whittled down to one. The whole experience can go on for two years, which means there is a huge amount of time in which to recover from their mistakes. Britain's more intense, four-week process leaves almost no room for error. "The American system gives you months to correct a mistake, but in Britain a mistake in a debate will have a much bigger impact. You do not have a lot of time to come back from it," Lehrer said. But he has one key piece of advice for Brown, Cameron and Clegg: always answer the question; don't waffle or avoid it, as viewers will spot it and punish you. "You must answer the question. Then you can explain the answer afterwards," he said. But it is not just verbal slip-ups that candidates have to look out for. In the era of television – especially in high definition – the candidates communicate with more than just words. "The body language of a candidate matters just as much as the spoken word," Lehrer said. That issue has also been amply illustrated in American debates. Al Gore sighed repeatedly during a debate with George W Bush, which played badly with viewers and led him to do less well against a debating opponent many had expected him to trounce. He duly lost the election. Most infamous of all was the performance of Richard Nixon, who was suffering from the flu and looked sweaty and pale during a debate with John F Kennedy in 1960. Television viewers thought Nixon lost the debate, while radio listeners thought he won it. Yet controlling such body language is notoriously hard, much harder than cribbing prepared answers. "A person is a person is a person. You are who you are and that comes out in debates," Lehrer said. He added: "It is dangerous territory. It is treacherous." Televised debates have become a key part of the US political landscape. Millions of viewers tune in to see the candidates vie for the White House. Since 1960 – the year of the first televised debate – they have become eagerly awaited as a sort of political sparring match. Lehrer believes that is because they offer a unique opportunity for the electorate to deal with all the candidates and all the issues in a single format. "It is a very revealing event," he said. "It is a lot like going to the butcher's store. You see all the cuts of meat on offer at one time." The other crucial aspect of presidential debates is the moderator. In Britain, debate organisers have followed America's lead and selected journalists more famed for their gravitas than their aggression. The BBC's moderator will be David Dimbleby, ITV has plumped for Alastair Stewart and Sky News has chosen Adam Boulton. John Humphrys and Jeremy Paxman, who are famed for their combative interrogations, have been conspicuously left out. Lehrer believes that is the right choice. Moderating a debate, he says, is not like conducting an interview. The moderator's job is to spur debate between the candidates, not catch a subject in a "gotcha" moment. "It is a moderating act. It is slightly different than being a journalist. At the end of the debate, if someone is talking about the moderator, then the moderator has failed to do their job." But moderating is not simply asking a question and waiting to see if the sparks fly. Lehrer said it was vital for a moderator to be able to roll with the answers given and not just stick to a script. The best moderators have to point out discrepancies and differences without inserting themselves too obviously into the process. "You don't want to be a robot, but your points should be aimed at getting the candidates to take on each other," he said. That might be why Lehrer's favourite debate was one between John Kerry and George W Bush in 2004. It did not change history or feature any headline-making quips, but Lehrer felt he had done his job well. "No one was talking about me; they were talking about the debate," he said. Still, Lehrer will admit to being pleased that Britain is following America's lead and scheduling debates between its political leaders. Though the process is intimately associated with American politics, he believes its appeal is universal and – more important – socially valuable. "It is good that it is spreading. It is just basically a good idea," he said.