Good question and one not easily answered!!
The electoral college choses the President .It is not decided by popular vote. . If the presumptive President is found ineligible before the electoral college votes then they can still vote and decide on who will be the President.Remember ;they are not committed to vote for the candidate selected by popular vote. Voters are only selecting electors to go the college vote. Electors most often vote the way the people of their state who sent them there wish ;but it is possible for them to change their vote even in cases when the candidate is eligible(see faithless electors... some states mandate that the electors vote for the candidate the state chose .but it is a state by state decision ) .
There are 2 example that can be used as a case study .In both cases it was not an ineligible candidate but a candidate who died after the elections but before the electoral college voted .
In the election of 1872 Democratic candidate Horace Greeley passed away before the meeting of the Electoral College; the electors who were to have voted for Greeley, finding themselves in a state of disarray, split their votes across several candidates, including three votes cast for the deceased Greeley. However, President US Grant, the Republican incumbernt , had already won an absolute majority of electors. Because it was the death of a losing candidate, there was no pressure to agree on a replacement candidate. Similarly, in the election of 1812, after the Republicans had nominated incumbent William Howard Taft and Vice President James S, Sherman, Sherman died shortly before the election, too late to change the names on the ballot, thus causing Sherman to be listed posthumously. That ticket finished third behind the Democrats (Woodrow Wilson)and the Progressive (Theodore Roosevelt)and the eight electoral votes that Sherman would have received were cast instead for Nicholas M Butler .
Electors pledged to a dead candidate
are free to vote for whomever they wish just as electors pledged to a live candidate are.
Electoral College (United States) - Wikipedia, the free encyclopedia
If the electors cannot decide with a majority then the President is selected by a vote of the House of Representitives. The 12th Amendment details the process. The House can only vote for the top three eligible recipients of Electoral College votes.
If the House of Representatives becomes deadlocked the 20th Amendment says the VP-elect becomes tempory President until the House of Representatives decides.
Look at Sec 3 of the 20th amendment carefully :
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.”
If the President-elect gets sworn in and then is found to be ineligible my best guess is that if if the President is not impeached and convicted that there would be a Constitutional crisis because no doubt the Supreme Court would be asked to get involved.
After being sworn in , the VP and a majority of the Cabinet ("or of such other body as Congress may by law provide"... ) could use the 25th Amendment and send a letter to Congress stating the President is unable to discharge the powers and duties of the office (Amendment XII includes the words "or other constitutional disability"), and force him to prove his eligibility there. But this would be unlikely since the founders intent to have the runner up serve as VP was changed by Amendment and a political ally of the President resides as VP.
BTW ;if the question is regarding McCain's eligibilty due to his place of birth it is a non-issue . He was born on US territory while his father served in the Panama canal zone. Regarding Obama's birth certificate ;
Currently, Title 8 of the U.S. CodeSec 1401 defines the following as people who are "
citizens of the United States at birth":
- Anyone born inside the United States
- Any Indian or Eskimo born in the United States, provided being a citizen of the U.S. does not impair the person's status as a citizen of the tribe
- Any one born outside the United States, both of whose parents are citizens of the U.S., as long as one parent has lived in the U.S.
- Any one born outside the United States, if one parent is a citizen and lived in the U.S. for at least one year and the other parent is a U.S. national
- Any one born in a U.S. possession, if one parent is a citizen and lived in the U.S. for at least one year
- Any one found in the U.S. under the age of five, whose parentage cannot be determined, as long as proof of non-citizenship is not provided by age 21
- Any one born outside the United States, if one parent is an alien and as long as the other parent is a citizen of the U.S. who lived in the U.S. for at least five years (with military and diplomatic service included in this time)
- A final, historical condition: a person born before 5/24/1934 of an alien father and a U.S. citizen mother who has lived in the U.S.
So even if the evidence shows that he was born outside the US and his Hawaii birth certificate was a fraud ;he would still be qualified .
I think I have answered all scenarios .