They have prevailed because the Democrats appeal to human stupidity and there's plenty of that in the American electorate (as you say, "what do you voters want, spinach or dessert?").
The Democrats are converting America from a Republic to a Democracy by appealing to the lowest common denominator.
The question is, can we reverse it when our schools and colleges are teaching kids that intelligence and wisdom ("math, science, hard work, punctuality, honesty, etc.") are racist?
Well put. An essential reality is that the left deploys "racism" as an effective shield to deflect any attempts to teach children or the electorate according to the lights of intelligence and wisdom.
Time to revisit nathanbedford's first maxim of American politics: all politics in America is not local but ultimately racial.

Life has been so easy in America for so long that Democrats had little trouble taking over with promises of free dessert for all - forever. As times get harder and they are forced to renege on all of those shiny promises, their only way out will be misusing the police powers of government to eliminate their critics.