Be clear • Trailing in the polls , Romney must defend himself, while also going on offense. He needs to reintroduce himself as a candidate with a clear vision who understands the struggles facing most Americans.
Egg him on • Romney will aim to provoke his rival. His campaign wants to create a moment that makes the president come across as smug like when Obama described Hillary Clinton as "likable enough" during a 2008 Democratic debate.
Play it cool • Romney needs to attack without appearing angry. "He needs to not confirm people's fear that he'sgot a nasty arrogant streak," says David Gergen, a Harvard University professor who has advised a bipartisan roster of presidents.
Be likable • Romney has higher negatives than Obama. This debate gives him perhaps his last best chance to reshape that image before the largest audience of the campaign.
Address the 47 percent • Romney must confront early on his secretly recorded "47 percent" remark, in which he described almost half the country as dependent on government benefits. He needs to reassure voters he cares about them.
Dodge distractions • No $10,000 bets. No talk of Harvard law school reunions. No "couple of Cadillacs."
What Obama must do
Play it safe • With the president clinging to a small to moderate lead, Rice University political scientist Paul Brace has this simple advice for him: "Don't screw up."
Show likability • One of Obama's big edges is voters like him more than Romney. He needs to remain genial, even when criticizing.
Woo 2008 backers • Romney's best chance to beat Obama is to win the votes of disappointed 2008 Obama voters. The debate gives the president a shot at winning them back.
Keep it short • The format lends itself to highlighting one of Obama's weaknesses ponderous answers so he must tighten his responses. His tendency to slip into professor-mode limits media-friendly sound bites that can stick with viewers.
Mine the middle • Obama will use his tax plan to charge Romney with being at odds with the interests of middle- and working-class voters.
Bring up Bain • Obama will raise Romney's work as head of the Boston-based company to spotlight the Republican's personal wealth. It's a topic the former private-equity executive doesn't always handle well.
With President Barack Obama ahead in the polls, Republican challenger Mitt Romney needs the debates to be a game changer. For advice on how to do well, he could look to one of the great GOP debaters, Ronald Reagan.
A second-by-second preview of what Romney will do at the debate
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Eight predictions about who will win the debate.
Will the debate be a game-changer?
Ann Romney's pre-debate words for Mitt: 'He's great. He's competent'