Associated Press

According to media reports, viewers can expect great drama in the first presidential debate as both candidates look to break away in the final month before the election. New Jersey Gov. Chris Christie predicted the race would be "turned upside down" by Thursday morning, while The New York Times' Nate Silver said the first debate may be Mitt Romney's best chance to turn the race around. The more realistic view, history suggests, is that the debate will have little impact on the election outcome. Political scientist James Stimson found little evidence of debate game changers in presidential campaigns between 1960 and 2000, the Washington Monthly reported, while political scientists Robert Erikson and Christopher Wlezien called the debate effect "fragile." "In other words, in the average election year, you can accurately predict where the race will stand after the debates by knowing the state of the race before the debates," reporter John Sides wrote. Here's a look at some "game changers" from past presidential debates.

John F. Kennedy vs. Richard Nixon, 1960
Associated Press

According to a CNN list of 10 debate moments that mattered, the meeting between John F. Kennedy and Richard Nixon in 1960 mattered because Nixon looked terrible.

"His makeup was bad. He wasn't feeling well. He looked sallow. He looked scornful. And people just reacted to that image of a vigorous, young Kennedy, and an almost sick-looking Nixon," the CNN article said.

Gallup data showed Kennedy moving from one point behind Nixon before the debate to three points ahead afterward. Stimson, Erikson and Wlezien found that Kennedy's margin after all of the debates was only slightly higher than his margin before the first debate.

"Given Kennedy's ultimate margin of victory in the popular vote of only two-tenths of a percentage point, it is clear the debates didn't produce a major shift in the structure of the election, but this debate-period boost in his support could very well have accounted for the outcome," Gallup posited.

» Watch the video here, or below.

Jimmy Carter vs. Gerald Ford, 1976
Associated Press

In a debate against Jimmy Carter in 1976, Gerald Ford said, "I don't believe that the Poles consider themselves dominated by the Soviet Union." The Washington Post called it a "costly debate misstep" in its list of the 10 most memorable moments in presidential debates.

However, Sides wrote, none of the debate viewers interviewed in one poll the night of the debate mentioned the statement when asked what each candidate had done well or poorly.

During the campaign, Carter lost a substantial lead over Ford, Gallup reported. He ultimately won the race with a two-point margin of victory.

"Carter's downward slide during the fall campaign seems to belie that this debate gaffe did much lasting harm," Erikson and Wlezien said.

» Watch the video here, or below.

Jimmy Carter vs. Ronald Reagan, 1980
Associated Press

Ronald Reagan entered into the 1980 debate against Jimmy Carter with a two-point lead a week before the election. After the debate, 44 percent considered Reagan to be the victor, while 26 percent said Carter won.

Gallup reports that without comparable pre- and post-debate registered voter figures on presidential preference, it's unclear what sort of impact the 1980 debate had, but since Reagan won the election by nearly 10 percentage points, "it is not likely to have been a determining factor."

Reagan had a five-point lead in the polls on the day of the debate or in the two days afterward, Sides wrote, meaning, "the debate seemed to matter, but it mainly nudged Reagan even further toward victory."

» Watch the video here, or below.


Michael Dukakis vs. George H.W. Bush, 1988
Associated Press

In 1988, Michael Dukakis was asked, "What would you do, given your feelings about the death penalty, if your wife, Kitty Dukakis, were raped and murdered?"

Dukakis' answer was given in what CNN called a "policy-wonkish way" that "underscored a vulnerability that he already seemed to be without emotion and without passion."

The Telegraph said the "manner of his answer, if not the substance, struck the wrong chord with voters."

Gallup, according to Sides, showed that the debates in 1988 had "little to no impact on voter preferences," while Stimson suggested they might have added a point to Bush's margins.

» Watch the video here, or below.

George H.W. Bush vs. Bill Clinton and Ross Perot, 1992
Associated Press

"It looked like he was bored, that he didn't care about the debate and that underscored the feeling that he wasn't connected to the problems of the people and the country," CNN said of George H.W. Bush's glance at his watch during a 1992 debate.

Although Bush explained the glance by saying he hated debates and was glad it was almost over, the exchange "fueled the contrast with Bill Clinton, who excelled at appearing to empathize more than the Republican," The Washington Post said.

That gaffe, and all of the debates of 1992, had little impact on Bush's standing, Sides wrote at the Washington Monthly. According to political scientist Thomas Holbrook, the second debate may have cost Bush about two points. The 1992 debates may have influenced voter support for third-party candidate Ross Perot more than they altered the structure of the race for Clinton and Bush, according to Gallup data.

» Watch the video here, or below.

Al Gore vs. George W. Bush, 2000
Associated Press

The debate between Gore and Bush in 2000 is an example of how body language can affect a campaign, the Telegraph said.

At one point in the debate, while Bush was answering a question, Gore got up and walked over to him, stopping close by. Bush nodded at him and continued his answer.

In other points during the debate, Gore would sigh. These sighs "came across as condescending," The Washington Post said. According to CNN, the sighs made Gore look like a teacher's pet who knew all the answers "but was annoying and irritating."

After the debate, there was a swing of two or three points toward Bush, which gave him a narrow lead, Sides wrote. As a whole, the debates in 2000 may have lowered Gore's poll standings about 2 points, Erikson and Wlezien estimated.

» Watch the video here, or below.