Republicans will likely try to paint the Illinois senator as a liberal and an elitist who is out of touch with mainstream America, the Los Angeles Times reported Sunday.
"The key is going to be whether Barack can avoid getting on defense on social 'wedge' issues and can stay on the offense on economic issues," said U.S. Sen. Claire McCaskill, D-Mo., an Obama supporter.
A recent Pew Research Center survey found that Obama is perceived by the public as more liberal than Democratic rival Sen. Hillary Clinton, D-N.Y.
The survey also found that most respondents said Arizona Sen. John McCain, the presumptive GOP nominee, is "a centrist whose views are fairly close to their own."
Obama has "handicaps and potential problems, race being one of them, (but) it's not the only one," Pew Center President Andrew Kohut said.
"He is perceived as a liberal. He is perceived by many voters as not well grounded on foreign policy and not tough enough ... and he has a potential problem, distinct from race, of being seen as an elitist, an intellectual."