Based on which party wins the statewide POTUS election in each of these three states.
This one should be almost as high as the chances of a Democrat winning North Carolina, since any situation where the Democratic candidate wins NC is one where they're also likely to win the other two. Betting it down to 4% makes no sense, unless you also think /ManifoldPolitics/which-party-will-win-the-us-preside-c2b132de8821 is extremely mispriced.
@PlasmaBallin I agree this is super undervalued. North Carolina almost flipped blue in 2020 and this time Biden doesn't have to share a ballot with a man who is famous for cheating on his wife. Polls are rough right now but November is a long ways away and Biden has made a serious investment in flipping NC. If he does as good or better than in 2020, NC is his mostly likely pick up.