The office of President of the Navajo Nation was created in 1991 following restructuring of the national government. The president and vice president are elected every four years, and can only serve two terms in office.
As outlined in the Navajo Nation Code §1001-1006, office holders have to be fluent in the Navajo language among other declared qualifications.
The Navajo Nation Code defines who may become or act as President upon the absence of a sitting president or a president-elect. Should the President, under circumstances outlined in the Navajo Nation Code at §1005(d)-1006, be unable to serve out his full term, then the Vice President shall act in his place for the remainder of the term, or until the President is able to resume his duties. §1006 of the Code instructs, that in the event a vacancy should "occur in the Office of President and Vice President, the Speaker shall serve as President of the Navajo Nation until a special election is held." The Speaker does not relinquish his Speaker duties whilst acting as interim President.