In Case of the Removal of the President from Office, or of his Death, Resignation, or Inability to discharge the Powers and Duties of the said Office, the Same shall devolve on the Vice President, and the Congress may by Law provide for the Case of Removal, Death, Resignation or Inability, both of the President and Vice President, declaring what Officer shall then act as President, and such Officer shall act accordingly, until the Disability be removed, or a President shall be elected.
The 25th Amendment altered the Constitution to determine that in cases of succession, the next officer (starting with VP) would become POTUS (a massive shift from the original intent of the Framers... a shift which began when His Ascendancy John Tyler made himself POTUS, as opposed to Acting POTUS). But no amendment altered the nature of those eligible to be on the order of presidential success... an Officer of the USA, more specifically of the Executive branch.
You posted a link to Wikipedia did you not? That article explicitly discusses the constitutionality issue in-depth. Did you not read it?
Article II, Section 1
The 25th Amendment altered the Constitution to determine that in cases of succession, the next officer (starting with VP) would become POTUS (a massive shift from the original intent of the Framers... a shift which began when His Ascendancy John Tyler made himself POTUS, as opposed to Acting POTUS). But no amendment altered the nature of those eligible to be on the order of presidential success... an Officer of the USA, more specifically of the Executive branch.
You posted a link to Wikipedia did you not? That article explicitly discusses the constitutionality issue in-depth. Did you not read it?