Romney to rehearse for fall debates

Mitt Romney will begin preparations for this fall's series of presidential debates this week when he goes head-to-head with a stand-in for President Barack Obama, a Romney campaign source said.

The source also said that the campaign has not yet decided whether Romney will attend any public events this week.

CNN reported last week that Sen. Rob Portman of Ohio has been tapped to aide Romney as the stand-in for President Barack Obama.

Portman described the role in an interview with CNN's Wolf Blitzer on Thursday.

"You try to get inside their head and figure out not just what they're going to say, substantively, but also how they're going to say stylistically," Portman said. "You try to be tougher than they [Obama] will be so that half way through the debate, Mitt Romney... says, 'it's not bad, I'm glad Portman is not out here on stage.' "

Romney and Obama will debate three times in October, and their running mates will debate once separately.

In addition to his seven terms in the U.S House, Portman's policy expertise includes service to the first Bush administration as counsel and director of legislative affairs, and to the second Bush administration as director of the Office of Management and Budget. He also held the post of U.S. Trade Representative and is in his first term in the U.S. Senate.

Romney officially became his party's presidential nominee this past week.