Without a contract, only the honest pay the downside.

If this is real, while bold, it's absolute retardation unless you have a written contract with very specific language. If not, you just took out a bet with + infinity odds. You'll never see a penny if Trump wins, especially when the media has already said they will ONLY call the election if it looks like Biden is winning. They won't even let Trump declare victory, it will have to go to the courts and your friend will simply use an excuse like he didn't win on election day, or it was a draw, or something else - and without a written contract defining the conditions of victory, you're screwed. That's if he doesn't just pull an "i was just kidding" on you. Without a contract, only the honest pay the downside.