"McCain has a hard time hiding his lack of respect for his opponent and we saw that in his debates against Mitt Romney where Romney really seemed to get under his skin," Alan Schroeder, author of the 2008 book "Presidential Debates: Fifty Years of High-Risk TV" and a professor at Northeastern University, told ABCNews.com.
"Obama's big problem is being able to really boil down his answers," Schroeder said, arguing Obama must guard against using lofty language or talking down to voters.
"What he's shown is that he's thoughtful in answering the questions and interacting with the moderators but he has to really try to connect directly with the broader audience of the tens of millions of viewers that'll be watching at home," Schroeder said.
Obama is expected to tout his early opposition to the war in Iraq and compare McCain's support for the war to Bush, who suffers from historically low job approval ratings.
McCain will likely highlight his early support for the U.S. troop surge strategy in Iraq, which has been credited in part with reducing violence there.
Presidential scholars say while McCain, a 26-year Washington veteran and war hero, is perceived by voters to have more foreign policy experience and to be more ready to be commander in chief, he must delicately explain his support for the war while trying to distance himself from the Bush administration's management of it.
"McCain can't sound like a cold warrior," said Wayne, a presidential scholar at Georgetown University.
"He can't sound too militant because I think that would rebound against him, given the current mood in the country, which is not to involve itself excessively in foreign entanglements," Wayne said.
Obama must convince voters that he can handle matters of national security, a perceived weakness for Democrats in general.
"[What] Obama has to be careful of is that he doesn't sound too verbose, that he's on point but no overelaborating the point and McCain has to sound cautious as well as confident," Wayne said.
Schroeder argued that McCain, 72, must also project energy in the marathon 90-minute debates against Obama, 47.
"It's a television show and you have to have that little extra energy going and I'm not sure that he necessarily displays that all the time," Schroeder said of McCain, noting that during the Republican primary debates McCain was always on stage with three or four other candidates and didn't have the kind of one-on-one sustained battles Obama had in the Democratic primaries with Sen. Hillary Clinton.
"This is almost like an athletic competition, so to be able to stand there for 90 minutes at the absolute top of your game is really hard to do and hard to do for anyone and of course both of these guys are tired to begin with because they've been at it so hard for so long," he said.
The Obama campaign has also quietly suggested in recent days that Obama may try to incite McCain's notorious short temper.
During his contentious 2000 Republican primary battle with Bush, McCain unloaded during a Columbia, S.C., debate.
"You should be ashamed, you should be ashamed," McCain told Bush. "You're putting out stuff that is unbelievable, George, and it's got to stop."
However, Schroeder said that while the pressure is intense for both candidates, a meltdown on live television is highly unlikely.