As of July 4th, three sitting Congressmen have called on Biden to step down.

But so far no Democrat Senators (50 of those) or state Governors (23 of those).
https://deepnewz.com/arizona/second-house-democrat-rep-grijalva-urges-biden-to-exit-presidential-race

The market will resolve YES if any of those 23 governors publicly call on Biden to step down, by the end of July [as judged by Eastern Time].

OR the market will resolve YES if Biden steps down

Otherwise the market will resolve NO.

Former governors, or governors of non-state US territories do not count.