(1) The Vice-President shall hold the office of President if the office of President becomes vacant by reason of death or resignation, impeachment, permanent incapacity or the removal of the President from office for any other reason in accordance with section 143 of this Constitution.
(2) Where any vacancy occurs in the circumstances mentioned in subsection (1) of this section during a period when the office of Vice-President is also vacant, the President of the Senate shall hold the office of President for a period of not more than three months, during which there shall be an election of a new President, who shall hold office for the unexpired term of office of the last holder of the office.
(3) Where the office of Vice-President becomes vacant:-
(a) by reason of death or resignation, impeachment, permanent incapacity or removal in accordance with section 143 or 144 of this Constitution;
(b) by his assumption of the office of President in accordance with subsection (1) of this section; or
(c) for any other reason,
the President shall nominate and, with the approval of each House of the National Assembly, appoint a new Vice-President.
Section 146 of the Constitution of the Federal Republic of Nigeria