President Biden.
Read the Constitution.
It isn’t, however I counter your argument to show me a ballot with president & vice-president separately.
Thus the swearing in of Obama and Biden to their positions would be itself null and void, and the vice-president would be Dick Cheny because the wearing in of Obama would have been itself illegitimate.
If you read the Constitution, nowhere doe it mention that the president and Vice-President should be elected together, yet THAT IS WHAT WE DO! (IE we’ve been ignoring the Constitution this whole time.)
Also, if I recall correctly the vice-president was the presidential candidate who came in second according to the unamended Constitution. It is because we amended that away that we have the possibility of a non-eligible vice-president.
To further make matters worst, the electoral college and the congress and even the general-public vote on a president/vice-president tuple instead of on the people individually.
It is for that reason that the invalidating of the presidential candidate would also invalidate the vice-presidential candidate... the ENTIRE election was fraudulent. The various secretaries of state should have verified the eligibility of each candidate before putting them on the ballot. (Thus every Presidential candidate would have to pass 50 official checks for eligibility.)