The meeting between John McCain and Barack Obama today at Saddleback Church in Orange County will be brief -- a handshake and perhaps an exchange of pleasantries in between back-to-back interviews with the church's pastor, Rick Warren.
But for the 3,000 people in the audience and viewers watching live on cable television, this first onstage matchup will offer a preview of the three critically important presidential debates, the first next month at the University of Mississippi.
Though appearing separately, the candidates will field similar questions about their faith, abortion, same-sex marriage and humanitarian efforts abroad. It is a chance for both to hone their comments on sensitive topics and practice connecting with an audience not chosen by their tightly controlled campaigns.
Debate analysts say that despite their different campaigning styles, neither McCain nor Obama will head into the debate phase with a clear advantage. "There's not such a great disparity in talent," said Northeastern University professor Alan Schroeder, author of "Presidential Debates: Fifty Years of High-Risk TV." "This isn't Bill Clinton versus Bob Dole."
Still, the campaigns have already begun trying to lower expectations. Obama spokesman Bill Burton noted that, with more than 20 primary debates, "we go into the fall, if nothing else, a tested organization." But he quickly added that McCain, after two decades in Washington, is "obviously a great debater." McCain strategist Charlie Black dryly noted that "in addition to being a great speechmaker," Obama "is pretty good on his feet."
In some respects, the candidates have opposite strengths.
Obama is often described as a powerful orator but was not a standout debater in the Democratic primary season. McCain is most comfortable speaking extemporaneously but has undercut his foreign-policy credentials with mistakes, such as mischaracterizing Iran's role in Iraq and referring to the Czech Republic as Czechoslovakia.
"This is like a high-stakes trapeze act that these guys have -- because mistakes and gaffes matter oh so much in these contests," said Tom Hollihan, a communications professor at USC's Annenberg School.
The two men will also have very different objectives in the three 90-minute presidential debates. McCain will try to convey his experience but must also show that "he has the energy and the forward-looking vision to lead" when matched with a much younger challenger, Hollihan said.
In addition, McCain faces the delicate task of energizing the Republican base while reaching out to independent voters disappointed in President Bush. "He has to deal with the ghost on the stage, and probably has to do that in a dramatic way," said Democratic strategist Bill Carrick.
By contrast, because of Obama's youth and relative inexperience, many undecided voters will use the debates -- along with forums like today's at Saddleback Church -- to assess the Illinois senator's preparedness for the presidency.
"The pressure will be on Obama," said Robert Friedenberg, a communications professor at Miami University in Ohio. With McCain likely to present himself as the "safe alternative," Friedenberg said, "people will be looking for [Obama] to demonstrate a mastery of the questions."
Past presidential contenders have learned, however, that debates can turn not just on substance but on how voters perceive small gestures or how a candidate answers a sensitive question. George H.W. Bush's decision to look at his watch three times during a 1992 debate with Bill Clinton and Ross Perot telegraphed to some voters that he'd rather be elsewhere.
Michael Dukakis' dispassionate answer in 1988 about whether he'd favor the death penalty if his wife were raped and murdered hardened some voters against him.
McCain's and Obama's extensive debate practice in the primaries may prove instructive.
Obama was widely viewed as improving as a debater -- and he may have learned from criticism. He was faulted in one debate for appearing to gang up on Sen. Hillary Rodham Clinton with John Edwards, and he took heat for what was widely interpreted as a snide remark to Clinton in a New Hampshire debate: "You're likable enough, Hillary."
McCain's difficulty is controlling his facial expressions. For him, there may be a cautionary tale in former Vice President Al Gore's sighs in his first matchup with George W. Bush in 2000 or in Bush's grimaces during his first 2004 debate with Sen. John F. Kerry.
McCain sometimes looked annoyed by his primary debaters, particularly former Massachusetts Gov. Mitt Romney, who "really seemed to get under his skin," Schroeder said.
"You can't do that in a general-election debate," he said. McCain's advisors are likely to work on "keeping him on an even keel at all times and not letting the situation rattle him in any way," Schroeder said.
By contrast, Hollihan noted that Obama generally appeared unruffled. "He very seldom lets his emotions get the better of him, which I think is very helpful," he said.