Thursday night's debate between George W. Bush and John Kerry on national security may well decide the presidential race. Voters harbor significant doubts about Bush--particularly on Iraq--but he currently holds a narrow lead because Kerry has not yet convinced voters that he is fit to be commander in chief. While Democrats would prefer to fight this election on domestic issues, where they enjoy advantages, in this time of uncertainty and war Kerry has to make people comfortable with his foreign policy leadership, or he will lose. This is his chance--perhaps his last chance--to make his case.

With that in mind, I asked U.S. Representative Adam Smith, the state chair of the Kerry campaign and a national security hawk, about what Kerry needs to do, and what viewers should watch for on Thursday:

1. Kerry must deliver a clear message that he understands the foreign policy challenges that face the country better than Bush does. The Republicans, beginning with the scurrilous Swift Boat attacks and continuing through their convention, have done a masterful job of tearing down Kerry in voters' minds. "Kerry's credibility has been placed specifically in question on foreign policy," Smith says. "He needs to convey that he will be strong enough, tough enough, and consistent enough to be the leader of the war on terror." He needs to talk about his determination to take on al Qaeda, to get Osama bin Laden, and to keep the Taliban from regrouping in Afghanistan.

2. Kerry must focus on the future more than on untangling the rhetorical mistakes he has made in the past. In substance, Kerry has had a consistent position on Iraq--he wanted to take out Saddam Hussein, if it could be done smartly and safely, but he did not support the Bushies' foolishly unilateralist rush to war--but he has muddled that message in recent months, opening himself up to the flip-flopper charge that Bush is hammering so relentlessly. Kerry has to answer that attack, but he can't get bogged down in playing defense. Instead, he needs to promote the idea that he has a plan to change the negative dynamic in Iraq, while Bush doesn't even understand he has a problem there.

3. That alone is not enough. Bush, because of his lead, can stick to just tearing down Kerry. Kerry has to build himself up and tear down Bush. Luckily, Kerry has a lot of material to work with. Iraq, as is obvious by now, is degenerating towards chaos and anarchy. Kerry needs, without sounding angry, to deliver a scorching indictment of how Bush's incompetence and disengagement from reality is responsible for that. "Bush has got to be held accountable," Smith says.

4. The debate doesn't end when the debate ends. Al Gore was initially thought to have won the first debate in 2000, but over the next 48 hours Bush's surrogates outspun the Dems, and perceptions shifted in his favor. That can't happen again. After the debate, "What we've got to do is pound Kerry's message home. Call bullshit on Bush in every medium. Whatever it takes," Smith says.