Throughout recent American history, televised debates have often played a crucial role in the outcome of presidential elections.
Televised presidential debates are a relatively recent development in the history of U.S. election campaigns.
The first televised debates were held during the 1960 election campaign between Democrat John Kennedy and Republican Richard Nixon.
Kennedy's youthful good looks and self-assured manner played well on television.
Vice President Nixon appeared to be in pain, suffering from a sore knee and a bad make-up job.
Kennedy: "I think it's time America started moving again."
Nixon: "The things that Mr. Kennedy has said, many of us can agree with."
Many experts believe that the debates were a crucial factor in John Kennedy's razor-thin victory in the 1960 election. Those watching on television gave Kennedy the edge. Similar surveys of those who listened on radio thought Nixon won.
Stephen Hess is an expert on the presidency at the Brookings Institution in Washington.
Mr. Hess said, "For example, in the very first one, when it was John Kennedy versus Richard Nixon, and Nixon was the much better known and more experienced candidate, but the attractiveness and the poise of John Kennedy actually convinced a lot of people in what proved to be such a close election that anything could make a difference."
Debates were not held again until 16 years later in the 1976 campaign between President Gerald Ford and his Democratic challenger, Jimmy Carter. In the second of three debates that year, President Ford made a comment that would come back to haunt him on Election Day: "There is no Soviet domination of Eastern Europe, and there never will be under a Ford administration."
Mr. Ford's gaffe about Eastern Europe may have been a deciding factor in Jimmy Carter's narrow victory that November.
Four years later in 1980, it was President Carter's turn to defend his record as an incumbent in a single debate with his Republican challenger, Ronald Reagan.
The two men were involved in a close race until Mr. Reagan asked this rhetorical question near the end of the debate: "Are you better off now than you were four years ago?"
The answer was apparently no, since the polls indicated a huge shift toward Reagan in the final weeks following the debate.
In 1984, Mr. Reagan ran for re-election and appeared somewhat unsteady and showing his age in his first debate with Democrat Walter Mondale. But the president seemed to recover with this quip in the second debate.
Mr. Reagan said, "I will not make age an issue in this campaign. I am not going to exploit for political purposes my opponent's youth and inexperience."
Walter Mondale said later he knew the election was lost the minute he heard the Reagan comment.
Presidential debates usually provide some of the main focal points in a campaign and draw millions of television viewers looking to assess the candidates before Election Day.
But sometimes what is important in debates is not what is said, but how it is said, and what personal insights they provide about the candidates. In the 1988 debates between then Vice President George Bush and Democrat Michael Dukakis, moderator Bernard Shaw posed this question to Governor Dukakis: "Governor Dukakis, if Kitty Dukakis were raped and murdered..."
In his answer, Governor Dukakis defended his opposition to the death penalty. But what many viewers remembered was the cold, unemotional way in which he talked about the prospect of losing his wife.
Other memorable debate moments have been seen, not heard. During one of the 1992 debates with Bill Clinton and Reform Party candidate Ross Perot, President Bush was caught on camera looking at his watch. That image seemed to buttress the view of some voters that the president was out of touch with the average person.
Four years ago, Mr. Bush's son, Texas Governor George W. Bush, faced off in a series of debates with Vice President Al Gore, who was considered the more experienced debater.
Perhaps the most memorable moment from that debate was a sigh of exasperation from Mr. Gore during one of Governor Bush's answers.
But Mr. Bush held his own against Mr. Gore and his better than expected debate performance may have been crucial in his narrow victory that November.
University of Virginia election expert Larry Sabato says this year's debates between President Bush and Senator John Kerry could also be critical.
Mr. Larry Sabato said, "The debates usually are not terribly important. But this year is going to be an exception. And it is an exception because it is a close, competitive contest and it is critical for the party nominee to energize partisans and get a large turnout of their base and also to attract an additional two or three percent they need among the undecideds and persuadable voters. Those are exactly the people who pay attention to debates."
Senator Kerry is counting on a good debate performance to close the gap in public opinion polls with President Bush. But the fact is, both candidates have a history of doing well in debates. Senator Kerry's debating skills helped win a tough re-election contest in Massachusetts in 1996 while President Bush exceeded debate expectations both in his 1994 victory in the Texas governor's race and in his contest against Al Gore four years ago.