Dog whistling refers to the art of making coded and often oblique and indirect but loaded references to race that stop short of expressions of personal hatred. The purpose of dog whistling isn't to express personal bigotry but to gain power, wealth and status. These messages convey a warning to white voters about presumed threats from non-whites aimed at building support for a reactionary agenda.
Example: Reagan building support among resentful white voters over the allegedly extravagant lifestyle or a mythical (nonwhite) "welfare queen." And using that support to undermine the middle class, attack the New Deal legacy and distribute wealth upward.
It's not personal...
Lopez has a great analysis for how the game is played. Here are the basic moves:
(1) punch racism into the conversation through references to culture, behavior, and class; (2) parry claims of race-baiting by insisting that absent a direct reference to biology or the use of a racial epithet, there can be no racism; (3) kick up the racial attack by calling any critics the real racists for mentioning race and thereby "playing the race card."Sadly, it seems to have worked pretty well for some folks for more than 30 years.