A lieutenant governor's responsibilities vary by state but generally include the following key roles:

• Serving as the first in line of succession to the governor’s office, meaning the lieutenant governor becomes governor if the current governor dies, resigns, or is incapacitated.
• Acting as the presiding officer or president of the state senate, often with the power to vote in the event of a tie and play a role in deciding which legislation advances. This parallels the vice president's role in the U.S. Senate.
• Holding duties in both the executive and legislative branches of state government, offering a unique combination of roles including legislative initiatives, testifying in various governmental capacities, and serving on governors' cabinets or state boards and commissions.
• Executing additional duties assigned by the state constitution, legislature, or the governor. These may include leading divisions or departments, overseeing specific state agencies (such as agriculture, rural development, tourism, or economic development), and chairing councils or task forces related to state priorities.
• Serving as acting governor when the governor is out of state or temporarily unable to serve, with corresponding powers during that time, especially in emergencies.

Examples of specific duties:

• In Indiana, the lieutenant governor oversees offices related to agriculture, tourism, defense development, and small business.
• In California, the lieutenant governor serves on various boards including the University of California Regents and state land commissions.
• In Virginia, the lieutenant governor presides over the Senate and serves on multiple state boards and councils.

Overall, the lieutenant governor's duties combine legislative leadership, executive responsibilities, and readiness to assume the governorship to effectively support state governance and continuity. The role's specific functions and power often depend on the individual state constitution and laws. The office is the second highest in state government and can be influential in policy and emergency management depending on the state.