Answer:
Prior to the passage of the 25th Amendment, if a vice president left office, the office remained vacant until the following election.
Step-by-step explanation:
The Twenty-fifth Amendment to the Constitution of the United States deals with the succession of the President of the United States, and establishes the procedures to be followed to occupy the position of Vice President in case this position becomes vacant, in addition to what must be made to find the president disqualified to continue in his position. It replaces the ambiguous text of Article II, Section 1, Clause 6 of the Constitution, which does not expressly state whether the vice president becomes the president, or if he acts as acting president (provisional) if the president dies, resigns, is ceased his office, or is unable for any reason to comply with the obligations of the office.