Some think that if a candidate is doing well or poor enough they won't bother to vote because it won't matter. Kind of like when everyone assumes someone else called 911 when there's an emergency.
Reagan was well liked and won by a landslide, I hate to say. By the time Bush Jr came around the mask was coming off.
Both Jr (-0.51%) and Trump (-2.09%) lost the popular vote when they were elected.
Hindsight being what it is, Reagan bad, Bush bad, Bush Jr bad, and Trump bad.
That's the fun part. The emitter is the detector. It will invert the beam of it detects anything.