With five weeks left until Election Day and Republican Mitt Romney slipping in the polls, the Romney campaign will hope to turn the tide starting Wednesday, with the first of three nationally televised debates against President Barack Obama.

Many political analysts say presidential debates rarely turn the tide in a race, calling it the exception, rather than the rule.

“In terms of it being a game-changer, it’s very rare that a political debate is going to change much about the (election) discourse,” said Benjamin Bates, an Ohio University professor who studies debate tactics and political communication. “It would have to be a fundamental error for people to change their minds.”

John Sides, a political scientist at George Washington University, wrote recently in Washington Monthly magazine that after extensive studies of debates, pre- and post-debate polling, and eventual election results from the past 50 years, “at best, debates provide a nudge in very close elections like 1960, 1980, or 2000.”

Underdog role

Whether the debates impact the election outcome or not, they do serve to shake up the monotony of campaign stops and attack ads, giving voters a new focus. And if voters are watching, that makes Wednesday important for Obama and Romney.

Both campaigns have been trying to position themselves as underdogs in the debate cycle, so that even a tie would be seen as a momentum-turning victory for their side.

During a Romney campaign stop in Dayton last week, Ohio Sen. Rob Portman talked about how he has played the role of Obama during Romney’s debate preparations.

“He’s a good communicator. We’ve seen that,” Portman said of Obama, calling him “formidable” and “a tough debater” last week. “I think he does a better job giving speeches than he does governing our country, frankly.”

Obama’s campaign has tried to build up Romney as a favorite as well, pointing to his debates in Republican primaries.

“Mitt Romney had many, many debates and he was very good in them,” Obama adviser David Axelrod told the Reuters news agency. “By and large when he needed to bring it, he did.”

What turns the tide

There are moments in presidential debate history that changed the way Americans viewed an election. And not all of them had to do with substantive politics.

Mark Caleb Smith, director of the Center for Political Studies at Cedarville University, pointed to the 1960 Nixon-Kennedy debates, saying the younger John F. Kennedy overcame perceptions of him as inexperienced and untested. Nixon also appeared surprisingly gaunt after being hospitalized for a knee injury — in contrast with his young, fit, tan challenger.

Bates pointed to the 1976 debate between President Gerald Ford and challenger Jimmy Carter, in which Ford said Poland was not under threat of Soviet influence.

“Then when the Soviets intervened in places like Poland, Romania and Yugoslavia, it made the public say, ‘Does Ford know what he’s talking about?’ ” Bates said.

Either side could suffer this year if one of their debate points turns around. Romney likely will keep hammering Obama about 43 months of unemployment over 8 percent. But with the national rate at 8.1 and new data due out two days after the first debate, Bates said that could backfire if economic news improves.

Obama, meanwhile, has been claiming that Americans are better off than four years ago, citing recoveries in jobs, housing and the stock market. But he could suffer if the recent stock market rally fades. A study by InvesTech Research shows that the direction of the stock market during the two months prior to the election has predicted the winner in 90 percent of presidential races since 1900.

Who has more on the line?

Smith said presidential challengers have more to risk and more to gain in debates, because the nation already knows the incumbent after four years in office. He said for Romney to take advantage, two things have to happen.

“First, a significant number of actually undecided voters have to watch,” Smith said. “Second … Romney, must effectively counteract an existing image. Romney will have to work hard to portray himself as understanding and sympathetic.”

Smith said Obama may go on the attack, as opposed to defending his own record, which is colored by a slow economic recovery.

Romney and Obama are likely to draw an audience Wednesday, as the debate will air on the four major networks, plus cable news channels. The three 2008 debates each had more than 50 million viewers. In comparison, Romney’s convention speech drew 30 million viewers, and Obama’s had 35 million.

Romney does appear to need a boost, as the past few weeks’ polls have shown him trailing Obama in almost every swing state, including Ohio. Smith said debates tend to reinforce the opinions voters already have, so Romney needs to break that trend.

Both Portman and Bates said despite all of the preparation, the debates will be valuable because they allow voters to see the candidates think for themselves.

“They have to look at each other, they have to respond to each other, and it’s the only opportunity we have to directly compare the two men who are seeking the presidency,” Bates said. “During that 90 minutes, the candidate is on his own.”

But if one of them falters, they can look to 2004 for inspiration. According to CNN polling, John Kerry won all three debates that year … and lost the presidency to George W. Bush.

Staff Writer Lynn Hulsey contributed to this report.