If Obama lied about his citizenship, not only should he be thrown in jail immediately, but every single travesty he has committed as President of the United States is null and void. No La Razans on the Supreme Court. No Communist Rubber Stamp Jurists who wouldn't even know how to wipe unless Obama told them. No 2000+ page Healthcare abomination. No Arizona lawsuit. None. Nada. Default, Game Over, this nightmare didn't happen.
I'm not sure about this. I may be wrong, but I believe the 20th Amendment would apply, and that amendment seems to look to the Vice President to be President.
Section 3. If, at the time fixed for the beginning of the term of the President, the President elect shall have died, the Vice President elect shall become President. 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.
Since in this situation described the President would not be able to qualify then I would imagine that Biden would simply be President. Of course, this does refer to qualifying while still not sworn in as it uses the term "President elect," and that may even mean that once sworn in the President is legitimate no matter what.
There is no president elect or vp elect at this time. The method for removing an ineligible president is impeachment- something that would never happen to the first black president.