"He's got to make Barack Obama the negative campaigner," Luntz said of Mitt Romney. He noted that Romney's favorability rating has risen since the first debate and the president's has stayed the same, which makes the negative attack a more precarious route for the president.
"If I am Barack Obama, I'm focusing on one number, and I'm trying to drive that 47 percent home as much as I possibly can," Luntz said.
Despite statements that the Obama campaign that the town hall format of the second presidential debate is difficult for the president, Luntz said, "It's not difficult."
"Everything you do is meant and is designed to interact with the people, and as president for the last four years, he has all these cameras on him."
"The challenge for Obama is in the pivot," Luntz added. "How do you pivot from talking about the way things are to what Romney has said and what Mitt Romney will do. The danger is when that pivot goes negative. And if Obama is seen as being the candidate on the attack, that's not good for him."
As Romney's support has increased, including in a new Politico poll that shows Romney with a 51 percent favorability rating, Luntz said he's paying the most attention to polls in the state of Ohio.
"Where Ohio goes is where American goes," Luntz said. "Mitt Romney should mention Ohio" during Tuesday's debate. "This is the only chance he has to do it."
Luntz said Romney must ask: "Not are you better off than you were four years ago, is America better off than it was four years ago."