The fierce and determined competitors in the tight race have a specific mission for the three debates, the first of which is Wednesday night in Denver.
Obama, no longer the fresh face of 2008, must convince skeptical Americans that he can accomplish in a second term what he couldn't in his first, restoring the economy to full health.
Romney, anxious to keep the race from slipping away, needs to instill confidence that he is a credible and trusted alternative to the president, with a better plan for strengthening the economy.
WASHINGTON (AP) -- New Jersey Gov. Chris Christie says says there's good news on the horizon for fellow Republicans, predicting that presidential candidate Mitt Romney is going to do "extraordinarily well" in the first debate with President Barack Obama on Wednesday night,
After that face-to-face meeting, Christie says "this whole race is going to be turned upside down."
Christie tells CBS' "Face the Nation" that every time Romney was backed into a corner during the GOP nomination fight, he "came out with a great debate performance because that's where he shines."Sen. John McCain says not to expect any surprises in this week's first presidential debate because the televised confrontations nowadays are so heavily scripted.
McCain was President Barack Obama's challenger in 2008. He says if he were running against Obama again, he could easily guess - and prepare for - the first half dozen questions because they are usually so obvious.
McCain says he still thinks debates are good for the country and the elections, and he predicted that Wednesday's debate between Obama and Republican Mitt Romney will attract the largest number of viewers in history.
McCain spoke Sunday on CNN's "State of the Union."
"Governor Romney - he's a good debater," said the president. "I'm just okay."
Mr. Obama held a twilight rally on a high school athletic field about 20 minutes from the Vegas strip, and said he's looking forward to the debate.
When he told the crowd, "folks in the media are speculating already on whose gonna have the best zingers," some supporters in the estimated 11,000-strong crowd shouted back: "You are."
The president arrived in this gambling mecca Sunday afternoon and set up debate camp at a luxury resort hotel just east of the city in Henderson, Nevada.
His preparations will include mock debates with Sen. John Kerry, D-MA., playing the role of Mitt Romney, though Kerry did not fly here aboard Air Force One.
President Obama's remarks on the debate reflected his campaign's strategy of trying to lower expectations for his performance.
"He has had less time to prepare than we anticipated," said Obama Campaign press secretary Jen Psaki "It's difficult to schedule significant blocks of time when you're the president, regardless of your party."
Like the president, she too portrays Romney as a more skilled and experienced debater, thanks to the 23 debates Romney was in during the primary campaign.
In rare praise of Romney, the Obama campaign spokeswoman said: "He's been disciplined and has been able to give short answers, so we know that's a strength."
Psaki said President Obama "has a tendency to give longer, substantive answers."
Citing reports that Romney has been prepping zingers to use against the president, Psaki said "that's not what the president's focus is on."
"So if you're expecting that, that's probably not what he's going to deliver on," she said of zingers by Mr. Obama.
She told reporters that he wants to use the debates to speak directly to the American people about his vision for "moving the country forward."
If true, it's a surprising strategy. Clever zingers are usually the basis on which pundits judge which candidates win, and the only thing - besides gaffes - that are remembered from the debates.