I believe the Constitution states that the VP elect takes the office.
Until new elections. It would be VP if he had to leave office due to illness, death, etc. But being ineligible makes the election fraudulent.
I would agree that the VP would take over......if the President had been sworn in. What happens if he is not sworn in and he is found to be illegal? The people didn’t vote for the VP....they voted for the President.
They haven’t been sworn in yet.
Section 3 of the 20th Amendment:
Section 3. .... If a President shall not have been chosen before the time fixed for the beginning of his term, or if the President elect shall have failed to qualify, then the Vice President elect shall act as President until a President shall have qualified; and the Congress may by law provide for the case wherein neither a President elect nor a Vice President elect shall have qualified, declaring who shall then act as President, or the manner in which one who is to act shall be selected, and such person shall act accordingly until a President or Vice President shall have qualified.
What the above means is that Biden would serve as President until a President shall qualify. But it does not say Biden would be President, only act as President. So we can certain there would be a new election.
What if Obama will not be certified by the Electoral College and Supreme Court will rule he's ineligible?