Twenty-second Amendment to the United States Constitution
As worded, the primary focus of the 22nd Amendment is on limiting individuals twice elected to the presidency from being elected again. Due to this, several issues could be raised regarding the amendment's meaning and application, especially in relation to the 12th Amendment, ratified in 1804, which states, "But no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States". While it is clear that under the 12th Amendment the original constitutional qualifications of age, citizenship, and residency apply to both the president and vice president, it is unclear whether someone who is ineligible to be elected president could be elected vice president. Because of this apparent ambiguity, there may be a loophole in the 22nd Amendment whereby a two-term former-president could be elected vice president and then succeed to the presidency as a result of the incumbent's death, resignation, or removal from office (or even succeed to the presidency from some other stated office in the presidential line of succession).
Acting President of the United States
Presidential succession is referred to multiple times in the U.S. Constitution, as well as the Twentieth Amendment and Twenty-fifth Amendment. The Vice President is the only officeholder named in the Constitution as a presidential successor. The Article II succession clause authorizes Congress to designate which federal officeholders would accede to the presidency in the event that the vice president were unable to do so, a situation which has occurred on three separate occasions. The current Presidential Succession Act was adopted in 1947 and last revised in 2006. The order of succession is as follows: the Vice President, the Speaker of the House of Representatives, the President pro tempore of the Senate, and then the eligible heads of the federal executive departments who form the president's Cabinet, beginning with the Secretary of State.