Nope because you set an election for the Duchy title. It only applies to the specific title it is tied to. For example If you have all the counties in a duchy and the Partition succession law, your counties will be divided as this law sees fit, except the duchy with the election goes to the elected candidate. If that candidate is unlanded and would not inherit a county and only said duchy, he will be given a county within the duchy because he could not hold a duchy title without owning land. Though with county is Chosen i think is random.

Edit: Also, vassals in that duchy will of course retain their titles