On November 28, many news sources said that Texas Republican presidential elector Art Sisneros, who doesn’t want to vote for Donald Trump, had resigned his position as a presidential elector. But, technically, he can’t do that; there is no provision for resigning.
What he can do is simply fail to appear in Austin on December 19. Presidential electors who don’t come to the meeting are deemed to have resigned, and to be replaced by the other electors. Thanks to Mark Seidenberg and Jim Riley for this information.
Those with a melodramatic imagination may imagine fanciful schemes in which presidential electors are kidnapped or otherwise prevented from attending such meetings.