Before first presidential debate, allies debate stakes

New Jersey Governor Chris Christie points as he delivers the keynote address to delegates during the second day of the Republican National Convention in Tampa, Florida, August 28, 2012.

WASHINGTON (Reuters) - Three days before the first presidential debate, allies of Barack Obama and Mitt Romney debated on Sunday how the encounter between the White House contenders will influence the U.S. election.

In typical straight-talking fashion, New Jersey Governor Chris Christie predicted fellow Republican Romney's performance at Wednesday's debate would alter the course of the campaign, weeks before the November 6 vote.

"This whole race is going to turn upside down come Thursday morning," Christie told CBS' "Face the Nation."

His comments strayed from the script of both campaigns, which have tried to play down their own candidate's chances at the debate in Denver and talk up their opponent, thus making it easier to claim victory or explain a defeat on Wednesday.

"I think what we need is a big and bold performance on Wednesday night, and that's what he's going to give us," Christie said of Romney on ABC's "This Week."

Romney comes into the first of three presidential debates with poor poll figures in important battleground states as he seeks to recover from a leaked video where the former private equity executive described nearly half of Americans as dependent upon government and who view themselves as victims.

"We've had some missteps, but at the end of the day the choice is really clear," Romney's vice presidential running mate Paul Ryan told "Fox News Sunday."

Ryan tried to lower the stakes for Romney's debate performance. "I don't think any one event is going to make or break this campaign," he said.

Obama departed for Nevada, where he will hunker down with aides in a "debate camp."

Obama was not focused only on scoring points or coming up with zingers to use against his rival, his advisers said.

"The president and Mitt Romney clearly view the debates as a very different opportunity. The President sees this as an opportunity to continue his conversation with the American people as he been doing over the last several months," campaign spokeswoman Jen Psaki told reporters on Air Force One.

GUARDING AGAINST COMPLACENCY

"He wants to speak directly to the families - the people who are on their couches at home, having snacks, drinking a beer, drinking soda, whatever it is, and tuning in for the first time - and that's who he's speaking directly to."

Obama was joined on Air Force One by White House adviser David Plouffe, campaign strategist David Axelrod, chief of staff Jack Lew, economic adviser Gene Sperling and speechwriter Jon Favreau.

The White House and Obama's campaign are guarding against complacency, with polls showing the Democrat ahead nationally by around 5 points, and much more in some swing states.

"We're not going to win battleground states by 10 or 12 points. This race is going to tighten.

"We've built a presidential campaign with a belief that it's going to come down to a few votes in a few states," Plouffe said on NBC's "Meet the Press."

Romney remained in Boston for private meetings, including debate preparation, at his campaign headquarters.

Not all of Romney's hours have been devoted to studying and sparring with his debate partner, U.S. Senator Rob Portman.

Romney attended a party Saturday evening at the Wellesley, Massachusetts, home of his finance chairman, Spencer Zwick.

With a stretched Hummer limousine blaring party music and several school buses parked outside the home, chants of "Mitt!" could be heard from within. Romney departs for Denver on Monday.

His wife, Ann, will campaign in Nevada and Ryan will embark on a bus tour of eastern Iowa on Monday.

Both are swing states, critical victories on the path to presidency.

(Additional reporting by Jeff Mason aboard Air Force One, Sam Youngman in Boston, Susan Cornwell and Bill Trott in Washington; editing by Alistair Bell and Todd Eastham)