Tell George W. Bush who lost the popular vote in 2000 but won the Electoral vote and was elected president that the Electors don’t choose the president! :-)
In contemporary times, candidates are vetted by: (1) having to campaign for a full year and do reasonably well in more than twenty primay election debates and 53 primary elections and or party caucuses to win a major party nomination; (2) clear placement on the state ballot by the Chief Elections Official, usually an elected Secretary of State, in 50 states plus the District of Columbia; (3) do reasonably well in three nationally televised presidential debates; (4) raise, at a minimum, half a billion dollars; (5) capture at a minimum, 60 million popular votes; (6) garner 270 electors; (7) have your electoral votes counted and certified by both Houses of Congress where any one Representative and any one Senator can submit to the President of the Senate a written objection to your electors. (8) Take the Oath of Office.
(9) Withstand any legal challenges to your eligibility that may be filed (Obama has had 226 legal challenges; 92 state and federal appellate court rulings and 27 appeals to the Supreme Court of the United States for a total of 345 legal challenges).
Succeed at each stage of the above and you too can be president.
The Electors, as I’m sure you know, don’t make a decision as to whether the candidate they’re pledged to is eligible, as the Founders no doubt intended. They are merely a formality by which the will of the voters, potentially somewhat distorted by the peculiarities of the winner-take-all system in most states, is expressed.
Since they no longer fill their original constitutional role, it defaults to the voters of each state.
Any state legislature, if it so chose, could return its own electors to what the Founders intended, choosing men who would exercise their own judgment on who to vote for. But that’s about as likely to happen as me being elected President.