The press is approaching tonight's debate with an eye towards whether Hillary Clinton improves over her last appearance, with some calling it a "defining moment" for her campaign. But Hillary's performance tonight is still only a sideshow to what's really important. As before, this debate is really part of the continuing contest to see who emerges from Iowa as Clinton's principal opponent - Edwards or Obama. The truth is that Hillary can afford to lose Iowa; the other two, especially Edwards, can't.

In the last debate two weeks ago, Edwards had his best debate so far. But in the aftermath of the debate, Obama won the interpretation contest - in part because the press, driven by the polls, continues to cover this race primarily as Clinton vs. Obama; in part because Obama astutely did some things - the Saturday Night Live appearance and the Jefferson-Jackson dinner speech - that boosted his campaign along the way. But, as the recent CBS/New York Times poll shows, it's still a three-way race in Iowa and right now, that's all that counts.

Given this background, here's what each of the three front-running candidates needs to think about doing tonight:

EDWARDS
Edwards needs to do pretty much exactly what he did before - consolidating his support on the Left and continuing to refashion himself as the Democrats' passionate "outsider" who has always been there for those in need. He could use a few more references to himself as the "real traditional" Democrat in the race (Obama did this skillfully in his Saturday night speech) and the more references to "Elizabeth and I," the better. He might want to trot out an electability argument at some point, since some recent polls show him running more strongly than the other two against someone like Giuliani in Ohio.

At this point, Edwards might want to tone down the attacks on Clinton (voters have gotten the point and negativity doesn't sell in Iowa) and he should definitely not attack Obama. At some point, that may be necessary but six weeks before the caucus is too early and Edwards doesn't want to get a reputation as just an attack dog. He also should be prepared for a question about his rather odd ad about taking health care away from congressmen, since it's unclear exactly how he could possibly do this.

OBAMA
The Obama campaign has a dilemma. It's clear that when Obama gets to speak to a large hall of over 9,000, he does an outstanding job. But he hasn't been able to transfer the energy of those performances on to television; even the televised coverage of last Saturday night didn't seem to capture what was going on in the hall - at least as observers on the scene described it.

As before, Obama needs to go to school - watching tapes of Gary Hart's 1984 debates to see how a cerebral candidate uses televised debates effectively. He should pepper his answers with the word "new" - "new ideas," a "new approach," a "new beginning." He should avoid attacking anyone, since it's inconsistent with his "new politics." And, as always, he should avoid the temptation to talk about himself. Instead, he should talk about the country and what he's learned. Talk people, not concepts. Tell stories, don't give policy prescriptions. Get fired up (not sure about ready to go).

CLINTON
It's an understatement to say that Clinton needs to do a lot better than last time. The good news for her is that it shouldn't be too difficult. For starters, it wasn't the other candidates who caused her problems last time; it was Tim Russert. Wolf Blitzer asks questions differently. Second, she's been good before, so all she has to do, really, is return to form.

To do that, she has to return to the style she assumed when she debated Rick Lazio for the Senate in 2000. (Historical footnote: The moderator was, you guessed it, Tim Russert.) When attacked, she should smile bemusedly and respond on the issues - not complain about how or why she's being attacked. The more specific she can be and the less she hedges, obviously, the better - a couple more waffles as in the last debate and she really will have a problem. Given the fact that she just changed her position on immigrants and drivers' licenses yet again yesterday, she'd better have that answer down straight and an explanation of why she's found that issue so difficult.

Equally as important, and as hard as it may be, she should try to have a good time. There's a certain tedious joylessness emanating from the Clinton effort. It's an overstatement to say that the most optimistic candidates always win, but this campaign could use a little more sunshine, a little more air. Hillary doesn't need to go wild and crazy but an occasional self-deprecating or humorous comment would do a lot to inject some life into her rhetoric.

To read Steven Stark's complete "Presidential Tote Board" blog, go to www.thephoenix.com/toteboard/