Final answer:
The president pro tempore of the state Senate would step in if the lieutenant governor had to assume the role of governor.
Step-by-step explanation:
If the lieutenant governor had to assume the role of governor, the leader who would step in as the leader of the state Senate is the president pro tempore. The president pro tempore is typically a senior senator from the majority party and takes on the duties of the lieutenant governor in their absence or if they are temporarily unable to act. This includes presiding over the Senate when the vice president is not available and acting in a largely ceremonial role, although the real power resides with the majority leader.