GOP presidential nominee Mitt Romney is "a good debater -- I'm just OK," Obama told supporters at Desert Pines High School in Las Vegas Sunday night.
"But what I'm most concerned about is having a serious discussion about what we need to do to keep the country growing and restore security for hardworking Americans," Obama said, leading into a stump speech.
Campaign spokeswoman Jen Psaki earlier told reporters not to expect home runs from the president during Wednesday's first of three debates.
"He wants to speak directly to the families of 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," she said.
Obama is preparing for the first 90-minute debate in Henderson, Nev., near Las Vegas, He is surrounded by top policy and communication advisers, including Chief of Staff Jack Lew, economic adviser Gene Sperling, political adviser David Plouffe, campaign adviser David Axelrod and political strategist Anita Dunn, the Los Angeles Times reported.
Sen. John Kerry, a rich, former Democratic presidential candidate from Massachusetts, is playing the part of former Massachusetts Gov. Romney during mock debates.
The first nationally televised debate, at the University of Denver's 7,200-seat Magness Arena, is expected to focus on domestic policy, with questions likely dealing with the economy, healthcare, "the role of government and governing," moderator Jim Lehrer, executive editor and former anchor of the "PBS NewsHour," said.
The final two debates are to take place Oct. 16 in Hempstead, N.Y., and Oct. 22 in Boca Raton, Fla.
The Obama and Psaki comments Sunday followed a New York Times report that Romney's team concluded the debates were about "creating moments," so aides have created a series of "zingers" Romney has been practicing on aides since August.
Romney's strategy includes seeking to lure Obama into appearing arrogant or evasive about his responsibility for the economy, the Times said.
Romney's sparring partner has been Sen. Rob Portman, R-Ohio, pretending to be Obama. The Times said Portman has gone after Romney repeatedly, to the point of being nasty, to get Romney worked up and then to show him how to keep his poise and look presidential.
Christie told NBC's "Meet the Press" Sunday, "Come Thursday morning, the entire narrative of this race is going to change."
Romney campaign officials distributed talking points to Republican allies and surrogates Sunday night outlining the campaign's message ahead of the debate.
The points say, "Obama doesn't have a record to run on or a plan for the future." They predict if Obama wins Nov. 6, "we will have four more years of the last four years, with a stagnant economy that fosters government dependency and a foreign policy that makes the world less safe."
By contrast, the points say, "When Mitt Romney is president, our nation will have pro-growth policies that foster upward mobility -- and lift people out of poverty -- and we will ensure peace through American leadership and strength."
They also say Romney would "not raise taxes on anyone, and he'll deliver tax cuts for the middle class."
The Romney campaign backed away to some degree from this point last week, with a campaign staffer telling The Wall Street Journal, "What we're proposing is a tax reform -- it's not a tax cut."
Romney himself told supporters in Westerville, Ohio, near Columbus, "Don't be expecting a huge cut in taxes, because I'm also going to lower deductions and exemptions."
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