Romney and Obama will be armed with competing numbers and visions

"In 2008, the first debate between Barack Obama and John McCain, one of the takeaways was McCain did not make eye contact with Obama," Schroeder said. "That came off as rude, disrespectful."

Part of the practice sessions is figuring out when to be aggressive and how to demonstrate leadership. It's also honing the lines from months of campaign speeches as the candidates get their final opportunities to speak directly to tens of millions of voters.

In the first debate, on domestic policy, Romney and Obama will be armed with competing numbers and visions.

"We will not surrender our dreams to the failures of this president," Romney told an audience in Bedford, N.H., last December. Expect the Republican to point to 23 million Americans out of work or underemployed, a national debt now at $16 trillion and three years of an unemployment rate above 8 percent.