HEMPSTEAD, NY — You've seen plenty of advice about what both candidates need to do in the second debate. What's more important are the pitfalls they need not skid into.

For Romney, there are three.

One is that he cannot be the Mitt Romney who does poorly at town hall meetings: starchy, uncomfortable, prone to weird asides and occasionally poor attempts at humor. Romney is a structure guy; the more structure a debate has, the better. The more questioners, with their body language and intonations, the more uncomfortable Romney will be. True, he's gotten better as he's campaigned, and he has done a lot of town hall meetings, and President Obama hasn't done a town hall meeting in awhile, but Romney is simply not in his element here.  

At the same time, he can't be the Romney who showed up and dominated debate number one. Then, he was the happy, confident warrior, easily parlaying questions into talking points and getting back to his core theme, using anecdotes from people he met on the campaign trail. This time, the anecdotes will be provided to him, and people who ask questions will want to hear them answered specifically. Romney HAS to be looser and more conversational, and he cannot "answer the subject," as he did so well in Denver.  

Third, he can't punt on specifics. If he does so, and this is pointed out to him by a questioner or a moderator, it will be a killer moment. The people selected by Gallup may be Democratic, independent, or Republican, but they collectively represent the reality-breaking particle of the debate. 

And what of Obama?

He will get a question or two that directly challenges his leadership. Not his policies or his decisions, but his leadership. And he needs a good answer, one that acknowledges the gravity of the situation he inherited, that concedes mistakes, but does not concede for a second the fundamental premise of his re-election campaign, which is that the country is getting better on his watch, and it will get "more better" if he is re-elected than if Romney wins. The leadership question will be killer. He cannot attempt a solid answer, because it will sound very thin. I don't know how I would answer the question, but that's why I'm not on the stage.

Obama does well at town hall formats, but as journalists have been wryly noting this week, he doesn't take questions from them often, and recently has surrounded himself by people who generally tell him what he wants to hear. He can't show irritation, either at the moderator, Candy Crowley, or at any questioner, no matter how provocative the question may be. Remember his mini "debate" with House Republicans at the beginning of 2010? He needs to summon THAT guy, and tone him down just a little.

Finally, he can't avoid the news of the day, which is probably going to be about Libya and Benghazi. He needs to take responsibility for the actions of his government, acknowledge that the truth of what happened isn't necessarily known just yet, and to remind voters that Republicans voted to cut hundreds of millions from the State Department security budget. He can't throw the question away like Vice President Biden did. In fact, the more obsequious Obama is, the better. Romney expects him to be defensive. He can't be defensive.