“There’s a difference between a governor leaving office, and a U.S. senator.
The governor can’t just be replaced by a person.”
The Lt. Governor assumes the duties in the absence of the governor.
“The Indiana Constitution states that the Lieutenant Governor:
1. Shall become Governor if the Governor resigns or dies in office, and Act as
Governor in the event of incapacitation of the governor (Art 5 Sec 10)”
https://www.nlga.us/wp-content/uploads/INDIANA.pdf