First ladies—unless you're Hillary, and that should say how much of a sleazeball Hillary is to be a first lady as disliked as she is—are pretty well-liked.
Michelle Obama is liked because she's associated to the Obama cult of personality. Never mind the fact that her hackneyed attempt to "healthify" school lunches left kids starving, all the while, her husband's administration was spiking food stamp usage through the roof, which is directly linked to poorer food decisions.
