The executive branch of the government of Puerto Rico is responsible for executing the laws of Puerto Rico, as well as causing them to be executed. Article IV of the Constitution of Puerto Rico vests the executive power on the Governor—whom by its nature forms the executive branch. The Constitution also establishes that the Secretary of State should serve as acting governor when the Governor is unable to perform his duties. The Secretary of State, therefore, performs an equivalent role to that of a Lieutenant Governor in United States politics.