Mitt Romney and President Obama face off in Denver at 9 p.m. in the first of three presidential debates. They have the power to reshape the race in its final weeks, if presidential history is any guide. YNN's Josh Robin explains why.

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NATIONWIDE -- The stage is literally being set. It could be this campaign season's most important 90 minutes.

"I do think that the debates could have a substantial impact on the election this time," said Republican consultant Brett O’Donnell.

Both sides agree that there's a greater burden on Mitt Romney than the president, who's leading in polls.

"People have to make the decision to fire Barack Obama and hire Mitt Romney and the challenge for him is that, you know, a lot of people like the President," said Neera Tanden of the Center for American Progress.

Tanden and O'Donnell would know. Tanden prepared Hillary Clinton four years ago. O'Donnell trained the last three Republican nominees, including Romney, during the primaries.

"I think both men are highly capable. Governor Romney went through 20 primary debates and in most of those debates, people thought he was the winner of those," O’Donnell said.

This time, Romney will likely pound Obama on the sour economy. Another advantage is that he'll almost be side to side with the President. He may need to unveil a major new proposal, if only to give a sense he's shaking up a campaign.

At the same time, he'll likely face queries about the famous video where he dismisses 47 percent of the population. Observers also say the Republican at last has to reveal a charm many say Romney is hiding.

Tanden said, "Even after all this time, this campaign has been going on already 18 months, people don't have a good sense of him or what he stands for."

Republicans are hoping to channel 1980, when a memorable one liner helped humanize Ronald Reagan and topple President Carter amid similar polls today.

Democrats see 1996, when President Clinton fended off Bob Dole.

Then there are the things this time Romney and Obama should avoid. It's the same thing for both candidates: Looking arrogant and out of touch. Crimes analysts say both men have committed."

Chances are both sides will say that they won the debate. That’s one bet you can safely make.