A common way to forecast election results is to estimate the probability of each state being the tipping point state and the probability of each candidate winning each state, multiply them together, and sum them. However, the probabilities of each candidate winning each state should really be conditional on that state being the tipping point state. This makes a difference because states that are considered likely to go to one party are probably less likely on the assumption that they're the tipping point state (e.g. Texas is likely Republican, but if it somehow ends up being the tipping point state, that makes it much more likely to go to Biden than it is currently thought to be). The reasoning behind this is basically, "If a state thought to be likely for one party actually ends up as the tipping point state, it probably went more towards the other party than we expected."

All options that are not the tipping point state resolve N/A. The tipping point state resolves based on whether it was won by the Democratic nominee. If that somehow isn't Biden, the title will change accordingly (this includes any situation where he's nominated at the convention but something happens to him before Election Day to cause him to be replaced by, e.g., Harris).

If there are two tipping points states, both of them will be resolved based on whether Biden wins. This situation occurs when one state would get him to 269 electoral votes, but another is needed to get to 270. See https://en.m.wikipedia.org/wiki/Tipping-point_state for details.

Note that it is possible for the tipping point state to be a Congressional district rather than an actual stare. However, in this case it is guaranteed that there would be two tipping point states.

See also: /PlasmaBallin/what-will-be-the-tipping-point-stat

/PlasmaBallin/will-states-will-be-bluer-than-the

(Note that the first of those markets defines tipping point state such that, if there are two of them, only the one that tips the winner over counts as "the" tipping point state, so it is slightly different from this market).