As President Barack Obama and Republican Mitt Romney take the stage at the University of Denver for the first Presidential debate of the campaign, there are a number of moments that have defined matchups in the past.

The Christian Science Monitor has come up with 7 defining moments in Presidential debates listed chronologically.

1960: John F. Kennedy vs. Richard Nixon

The first televised Presidential debate was not kind to Richard Nixon. John F. Kennedy appeared to be tan and fit while Nixon, who refused to wear makeup looked haggard and tired with a Five o'Clock Shadow. The race turned in Kennedy's favor after the debate although many who listened on the radio have said they felt Nixon won the matchup.

1976: Gerald Ford vs. Jimmy Carter

President Gerald Ford made a memorable gaffe during his debate with then-challenger Jimmy Carter when the cold war was brought by panelist Max Frankel of the New York Times.

“I don't believe, Mr. Frankel, that the Yugoslavians consider themselves dominated by the Soviet Union,” Ford replied. “I don't believe that the Romanians consider themselves dominated by the Soviet Union. I don't believe that the Poles consider themselves dominated by the Soviet Union. Each of those countries is independent, autonomous: It has its own territorial integrity and the United States does not concede that those countries are under the domination of the Soviet Union.”

1980: Jimmy Carter vs. Ronald Reagan

Ronald Reagan's previous political and acting experience served him well in his matchup with President Jimmy Carter.

Reagan also uttered one of the most memorable and oft-used debate lines. “There you go again,” Reagan famously quipped, defusing Carter’s repeated criticism of his initial opposition to Medicare legislation.

Reagan trumped Carter at numerous points during the debate, especially after Carter made the mistake of saying that he asked his daughter, Amy (then age 13), her views on the most important issue facing the nation. (She said nuclear proliferation.)

1988: George H.W. Bush vs. Michael Dukakis

Massachusetts Governor Michael Dukakis' cold answer to a passionate question was his downfall in this debate.

Moderator Bernard Shaw from CNN opened the debate with a question about the death penalty. “Governor, if Kitty Dukakis were raped and murdered, would you favor an irrevocable death penalty for the killer?” Mr. Shaw asked.

“No, I don't, Bernard,” replied Dukakis, without a pause.  “And I think you know that I've opposed the death penalty during all of my life. I don't see any evidence that it's a deterrent, and I think there are better and more effective ways to deal with violent crime.”

1988 Vice Presidential Debate: Dan Quayle vs. Lloyd Bentsen

Dan Qualyle was constantly hounded by questions about his experience and ability to take over as President if needed. The issue was raised in their debate.

“I will be prepared not only because of my service in the Congress, but because of my ability to communicate and to lead,” Quayle said. “It is not just age; it's accomplishments, it's experience. I have far more experience than many others that sought the office of vice president of this country. I have as much experience in the Congress as Jack Kennedy did when he sought the presidency.”

His opponent, Sen. Lloyd Bentsen (D) of Texas, shot back: “Senator, I served with Jack Kennedy, I knew Jack Kennedy, Jack Kennedy was a friend of mine. Senator, you are no Jack Kennedy.”

1992: George Bush vs. Bill Clinton (and Ross Perot)

Both Ross Perot, running as a third party candidate, and President Bush had their moments in their debates.

Mr. Perot had several memorable lines: “The party is over and it’s time for the cleanup crew.” “I don’t have any experience in running up a $4 trillion debt. I don’t have any experience in gridlock government where nobody takes responsibility for anything and everybody blames everybody else.”

But the defining moment of the Bush-Clinton-Perot debates was an unconscious gesture by Bush: During the second debate in Richmond, Va., on Oct. 15, 1992, Bush checked his watch – twice.

2000: George W. Bush vs. Al Gore

Al Gore's body language was an issue in their first debate that hounded him through all of their debates.

Gore "sighed heavily and repeatedly. He shook his head, frowned, rolled his eyes, and sneered," wrote Lehrer in his book "Tension City.”

“Gore was judged the clear loser in the debate, based almost entirely on his body language and not on what he actually said," he added.

Although Gore tried to change his style for the next two debates, he could not escape the first debate mannerisms – the late-night comedy shows repeatedly mocked them.