The president needs to do three things in Denver well.  First, he needs to show some emotion about the struggles facing the American people, from the wounded warriors and their families to the unemployed. Obama told author Michael Lewis that he doesn't like to fake sincerity.  He doesn't have to; he needs to method-act: to connect to the feelings he has when each night he reads the letters of average Americans, or when he visits the wounded at Walter Reed.

Empathy is a powerful sword and shield against Romney.  The president is already seen as more empathetic than Romney, but he needs to accentuate that gap during Wednesday’s debate. And showing concern can help defend against Romney's central argument: The president is a failure, and we can't afford four more years of him. In addition to countering, as he usually does, with his own facts, the president needs to remember who he is fighting for and tell Romney in so many words: "I can tell you, Mr. Romney, that the toughest criticism doesn't come from you; it comes from myself. I know our economy isn't where it needs to be. I know that coming out of the worst recession in 80 years and 18 straight months of job growth doesn't mean a thing to the person who still can't find work; or that killing Osama Bin Laden doesn't make a mother with a son or daughter in Afghanistan feel any less anxious. I know that because I've talked to many Americans who are still suffering and struggling. Nobody in my administration is satisfied.  But we also know that we're in this together.  All of us.  We can't be strong if we write off millions of Americans, if we just invest more in the wealthy and forget about the middle class. As Huck Finn said, We've ‘been there before,’ and, as he might have added, ‘ain't going back.’ ”

Second, Obama should follow the example of the greatest boxers, such as Muhammad Ali and Sugar Ray Leonard, who would often completely change their style of fighting from bout to bout to befuddle their opponents. Instead of continuing to attack Romney only for his plutocratic policies, Obama should reintroduce the flip-flopper argument. Romney might not be as prepared for this, and it makes an effective counter to Romney's attacks that Obama has broken his promises to the American people. Obama can point out that he has made progress despite considerable opposition and odds because he has been steadfast in his principles, in contrast with Romney whose principles seem easily morphed.

Finally, Obama could perform a public service as well as put Romney  on the defensive if he could find out which deductions Romney will eliminate for the middle class to lower their tax rates. Mortgage interest? State and local tax deductions?  It may be hard for Romney to keep hiding on that one.