Eight years ago, a Quinnipiac University poll showed incumbent Mayor Michael Bloomberg leading his Democratic challenger, Fernando Ferrer, by 31 points. When WABC-TV hosted a debate between the two, The New York Times' Clyde Haberman asked, "Who do they think will be watching?"

We might ask the same about tonight's debate, the first televised face-off between the major party candidates for mayor. Unfortunately for Republican nominee Joe Lhota, however, we already know the answer. The people who tune in tend to be those most interested in politics -- in short, those who've already made up their minds.

Still, the debate is critical for Lhota; it's his last great hope to shake up the race. Viewership of future debates will almost certainly drop off. If he has any hope of moving the needle, tonight he must:

1. Maximize news coverage. Since those who watch are likely to leave it more committed to their original candidate, Lhota needs to appeal to important reporters, editors and editorial boards, in the hope that they will spread positive news about his candidacy.

2. Reinforce his campaign theme, 5 boroughs, 1 city. Lhota can't afford to simply repeat what he's said before; since his goal should be to get news coverage, he should avoid rehashing statements from his stump speech.

3. Focus on his image as well as the issues. Lhota is still something of an unknown to voters. So he needs to let New Yorkers know not only what kind of person he is, but also what kind of leader he'll be.

4. Most important, Lhota needs to show he understands the aspirations, hopes and dreams of average New Yorkers better than Democrat Bill de Blasio. And he must also demonstrate that he has the personality, leadership style, ideas and knowledge to help them.

Even if Lhota does these things, he has an uphill climb. Ferrer couldn't do it even with a Democratic enrollment advantage.

Lhota's job is even tougher. Not only does he need to close a larger gap -- 50 percentage points in a recent poll -- but he also has to do it as a Republican in a city that is still overwhelmingly Democratic.

It is not an impossible task, but it is formidable and time is running short.Jeanne Zaino is professor of political science at Iona College and of political campaign management at New York University.