University of Denver students Zach Gonzales, left, and Dia Mohamed shake hands Tuesday as stand-ins for the candidates at a rehearsal for the first presidential debate, which is to be held Wednesday night in Denver. The campaigns use stand-ins of another sort to help candidates practice their arguments. (SAUL LOEB, AFP/Getty Images / October 2, 2012)

When President Barack Obama and Mitt Romney debate one another for the first time Wednesday night, they may feel as though they've already done so.

As with stage lighting and cameras, stand-ins are also commonly used in debate preparations, and the faux opponents perform a crucial job, says Irving Rein, a communications professor at Northwestern University.

"You pretty much know what the questions are going to be," he said. "The key is the follow-up."


To play the role of his Republican opponent, Obama picked Sen. John Kerry of Massachusetts, the 2004 Democratic presidential nominee. Romney stuck with Sen. Rob Portman of Ohio, who also was 2008 GOP presidential nominee John McCain's pick to stand in for Obama.

As for the vice presidential stand-ins, former Solicitor General Ted Olson is playing Joe Biden and Rep. Chris Van Hollen of Maryland is playing Paul Ryan.

Stand-ins remind candidates that memorizing answers and catchy sound bites is only part of the prep work.

"If the stand-in is good, he or she will be able to emulate what might happen in terms of a follow-up by the opponent," Rein said. "The stand-in plays a critical role in asking a question or responding in that interactive exchange that you just can't get by asking the candidate a question."

The first of three presidential debates is Wednesday night, at the University of Denver.

Alan Schroeder, a journalism professor at Boston's Northeastern University, says campaign strategists hope to prepare their candidate for every possible turn of events during a debate. Stands-ins must not only learn the various policies and positions of the candidates they are portraying, they must also learn their stage habits and rhetorical techniques.

"By doing mock debates, what they're really trying to do is buy an insurance policy against the possibility that something might go wrong," said Schroeder, author of "Presidential Debates: Fifty Years of High-Risk TV."

Mock debates have remained routine for presidential candidates since the 1976 election, when Gerald Ford pioneered the practice, according to Schroeder's book. When a live stand-in wasn't available, Ford debated a TV monitor that played clips of his Democratic opponent, Jimmy Carter, from interviews on "Meet the Press."

"Over the years, it's just become more and more part of the ritual," Schroeder said.