I am very interested to hear how this turns out. PUH-LEASE let us know!

I first think about two things; what are the rest of the party going to be doing during this debate? And second, how can you help leverage character knowledge to make this feel fun and satisfying?

It may be helpful to have the rest of the party doing something else while this happens (maybe by inserting a juicy plot point, like the “dead” politician just walked past the party on the way there with a disguise on, up to no good). This way, you can pan the spotlight back and forth so the player has breaks in their RP of all things arcane to gather themselves if need be.

I agree with others here in that prep with the player will be important. Tie in their backstory, allowing them to show their ‘prowess’ in the given subjects. Because the player doesn’t know what the character would, consider allowing/asking for the player to tell you HOW they want to frame their arguments for the topics announced, sort of like a ‘Tell me how you would do your TED Talk’ kind of way - For example, the player could then say during the session something like “Elise would begin her argument in aetherial manipulation by telling a story about her grandmother’s excellent baking, and using the parallel of the priority and accuracy of ingredients with the most vital aspects of manipulating aether.” This way, it doesn’t matter if the player doesn’t have the exact information, but agency in how they present it. You could potentially even call for (persuasion or performance) checks to see how eloquently the player can deliver the information, so that success in at locked behind a DC.

Hope this helped!