Craig, one of Obama's few gray-haired advisers, defended former President Clinton during his impeachment proceedings.
The first of three presidential debates before Election Day will be held at the University of Mississippi and moderated by PBS' Jim Lehrer.
The second presidential debate, hosted in partnership with social networking Web site MySpace, will be a town hall-style debate held in Nashville, Tenn., with moderator Tom Brokaw. Some voters will have the chance to ask questions. The third presidential debate at Hofstra University in Hempstead, N.Y., will be moderated by CBS' Bob Schieffer and focus on domestic and economic policy.
Friday's debate is expected to be the most watched of all the debates this year, and with interest in this election high, it could gain more viewers than the 62.4 million people who tuned into President Bush's debate with Sen. John Kerry in 2004.
Obama Campaign Seeks to Lower Expectations
In an effort to raise the stakes for McCain this week, the Obama campaign has argued that the Arizona senator holds the advantage when it comes to foreign affairs and that he needs a knockout to win.
"John McCain has boasted throughout the campaign about his decades of Washington foreign policy experience and what an advantage that will be for him," Obama spokesman Nick Shapiro told ABCNews.com. "This debate offers him major home court advantage and anything short of a game-changing event will be a key missed opportunity for him."
Holding McCain's game plan close to its chest, the McCain campaign didn't respond to inquiries from ABCNews.com about the debates.
Presidential historians argue that this first debate will be a key test for Obama. The Illinois senator is widely perceived to hold an advantage on the economic and domestic issues that will likely dominate the next two debates on Oct. 7 and Oct. 15.
"As we saw last week Obama has a clear advantage on the economy issues, so if he can diffuse the national security issue, which has been Sen. McCain's strong suit, then I think going into the home stretch he probably establishes a clear if small advantage overall," presidential historian Richard Norton Smith told ABCNews.com.
"For McCain it's an opportunity after a bad week and with the economic issues trending against him to get back into the game and to eliminate the gap that exists right now in the polls," Smith said.
Debate scholars who have studied both candidates' previous debate performances argue both candidates have weaknesses going into the debate, exposed by multiple primary debates.
"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.
McCain Perceived to Hold Advantage in Foreign Policy Debate
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.
Age Issue, Temper May Advantage Obama
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.
"The Obama campaign would love to see McCain blow up in the debate but I don't think that's going to happen," Schroeder said. "McCain is a very seasoned politician. He knows that he can't lose it on international television in front of 75 million people."
VP Debate Pits Media-Shy Palin Against Talkative Biden
The highly anticipated vice presidential debate between Democrat Joe Biden and Republican Sarah Palin will be held Oct. 2 at Washington University in St. Louis, Mo., moderated by PBS' Gwen Ifill.
Biden has been preparing for the debate by practicing against Gov. Jennifer Granholm of Michigan.
Biden, a two-time presidential contender and longtime Delaware senator, holds a clear advantage over Palin going into the debates, scholars say.
However, some scholars suggest that with expectations low for the Alaska governor, she may hold an advantage.
"In any discussion with Sarah Palin, if she looks as good as her opponent then she wins because she lacks the experience," Wayne said.
But Schroeder argued that by only allowing Palin to do a handful of interviews, the McCain-Palin campaign may be making a strategic error.
"With Palin it's just that we've seen so little of her and if they continue to withhold her, then it really puts her under this enormous pressure to perform, because people are really curious to know, why hasn't she been doing many one-on-one interviews," Schroeder said.
But, he said, "she is obviously very quick with the one-liners and obviously knows how to work the camera, so I see her as having a lot of advantages in some ways."
Scholars said Biden has a reputation for talking too much and may be constrained by the vice presidential debate format that will force him to compress his answers. "He sometimes has a hard time getting to the point and of course the thing, too, is how does he treat her, and I think a lot of people will be watching for the dynamic between the two of them," Schroeder said.
Any perceived gaffes will be replayed over and over.
During the 1988 vice presidential debate between Dan Quayle and Lloyd Benson, Quayle, who was perceived to lack experience, made a historic gaffe by seeming to compare himself to former President Kennedy.
"I have as much experience in the Congress as Jack Kennedy did when he sought the presidency," Quayle said, to which Benson historically responded, "Senator, I served with Jack Kennedy: I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."
Style Often Trumps Substance in Modern Televised Debates
McCain, who feels more comfortable in town hall-style formats, challenged Obama to a series of town hall debates this summer, but negotiations between the campaigns fell apart and Obama declined.
Presidential scholar Stephen Hess of the Brookings Institute argues that style has often outweighed substance in the modern era of televised presidential debates.
"How well they do is going to depend on how confident they looked and whether their messages were punchy or not," Hess told ABCNews.com.
While some political analysts say modern presidential debates have devolved into which candidate has the best sound bite, others argue debates give the candidates an opportunity to demonstrate their knowledge on issues.
"Aside from the conventions, the debates are the only time most Americans are going to watch McCain and Obama for an extended period of time -- a period of time that allows them to make judgments about their character, their sense of self and how they handle themselves and their adversaries in stressful situations," said former White House political director Sara Taylor, a Bush-Cheney deputy strategist in 2004.
Some presidential debates have had an impact when elections have been very close like this one, and can be game changers.
During the 1960 presidential debate between Kennedy and then-Vice President Richard Nixon -- where famously people on the radio thought Nixon had won while voters who watched the debate on television said Kennedy had won -- Nixon was widely assumed to have a leg up on foreign policy issues.
"That debate was pivotal in elevating Kennedy to Nixon's level and overnight diffusing the experience argument," Smith said.
However, Smith cautioned against putting too much emphasis on who is perceived to come out on top after the debates.
"Four years ago all the polls indicated that Sen. Kerry won all three debates," Smith said, "and it didn't help him on Election Day."
Slideshow archive | ABC13 wireless | Help solve crimes