The lieutenant governor serves as acting governor when the governor becomes incapacitated.
In the state's early history, lieutenant governors would serve as acting governor while the governor was away from the capital.
Christopher Harrison was the first lieutenant governor to serve as acting governor while Jonathan Jennings negotiated treaties far from the capital.

If the governor dies in office, becomes permanently incapacitated, resigns, or is impeached, the lieutenant governor becomes governor.
In total, ten lieutenant governors become governor by succession.
The first occurrence was when Jonathan Jennings resigned to become a congressman and was succeeded by Ratliff Boon.

In the event that both the governorship and lieutenant-governorship are vacant, the constitution stipulates that the Senate President pro tempore becomes governor.
Historically, governors appointed the pro tempore to serve as acting lieutenant governor as a formality.
This practice ended in the early twentieth century.
 Although the constitution did not specify a method to fill a vacancy in the lieutenant governorship, an attempt to fill a vacancy occurred in 1887.
When the winner of the election attempted to be seated, the Senate erupted into violence known as the Black Day of the General Assembly; the lieutenant governor-elect was sworn in but never seated.

Should the lieutenant governorship become vacant for any reason, including death, resignation, or succession, the governor may nominate a replacement who must be approved by both houses of the General Assembly.
The lieutenant governor serves as acting governor when the governor becomes incapacitated. In the state's early history, lieutenant governors would serve as acting governor while the governor was away from the capital. Christopher Harrison was the first lieutenant governor to serve as acting governor while Jonathan Jennings negotiated treaties far from the capital.
If the governor dies in office, becomes permanently incapacitated, resigns, or is impeached, the lieutenant governor becomes governor. In total, ten lieutenant governors become governor by succession. The first occurrence was when Jonathan Jennings resigned to become a congressman and was succeeded by Ratliff Boon.
In the event that both the governorship and lieutenant-governorship are vacant, the constitution stipulates that the Senate President pro tempore becomes governor. Historically, governors appointed the pro tempore to serve as acting lieutenant governor as a formality. This practice ended in the early twentieth century.  Although the constitution did not specify a method to fill a vacancy in the lieutenant governorship, an attempt to fill a vacancy occurred in 1887. When the winner of the election attempted to be seated, the Senate erupted into violence known as the Black Day of the General Assembly; the lieutenant governor-elect was sworn in but never seated.
Should the lieutenant governorship become vacant for any reason, including death, resignation, or succession, the governor may nominate a replacement who must be approved by both houses of the General Assembly.
Lieutenant Governor of Indiana