If someone says something like, “Biden shouldn’t step down but if he does then I should be the presidential nominee” (much like Cruz Bustamante in the 2003 California recall), that doesn’t count.

The deadline here is Election Day — or, if Biden announces he is actually dropping out, it must be before that. 

General policy for my markets: In the rare event of a conflict between my resolution criteria and the agreed-upon common-sense spirit of the market, I may resolve it according to the market's spirit or N/A, probably after discussion.