22nd Amendment
No person shall be elected to the office of the President more than twice, and no person who has held the office of President, or acted as President, for more than two years of a term to which some other person was elected President shall be elected to the office of the President more than once. But this article shall not apply to any person holding the office of President when this article was proposed by the Congress, and shall not prevent any person who may be holding the office of President, or acting as President, during the term within which this article becomes operative from holding the office of President or acting as President during the remainder of such term.
So let’s say in 2016, the Democrats nominate Michelle Obama as President and Barack Obama as Vice President. Michelle is sworn in after being “elected” by the Electoral College, then immediately resigns. Barack Obama would not have been “elected to the office of President”.
Now the twelfth Amendment (passed shortly after the country was founded) adds “But no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States.”
So who has standing to challenge VP Barack Obama?
Egads! Some conspiracies make me cringe in terror. This one qualifies.
I remember this concept floated that maybe Hillary would become a defacto third term for Bill Clinton. I think this idea popped up while listening to a local talk show host.