Something along the lines of "Nate Silver tweeted bad things about Biden to move a market", or "Nate Silver intentionally manipulated his model to cause large swings", or "Nate Silver paid by the RNC to make critical tweets". In short, the scandal must be big enough that nearly everyone discredits him.

Something like "Nate Silver bets on the outcome on his model" will not count

Must be public before close date. I will not bet in this market (except for base rate setting)