Setting up a debate attracts folks because they expect a "fight" or at least a disagreement. They also feel that they will be hearing "both sides." It could be a formal debate or just a panel with opposing points of view. You might get your school debate team to take on public financing (Fair Elections) as a topic for a formal debate that you will publicize with them.
Here are some ideas for topics:
Is America a Democracy?
Public vs. Private Financing of Elections
Who are our Representatives Representing? Us or Them?
Corporate Control vs. Democracy
Democrats vs. Republicans vs. Greens etc. position on Environmental or Foreign or Educational Policy, etc.
Be sure to have sign up sheets and Democracy Matters literature available for attendees.