This election was indeed about the economy, immigration, and security. That is not what the Democratic leadership thought it was about. That was their strategic mistake.
Democrat operational mistake One
D messaging: "Bad Trump, Bad Trump, Bad Trump".
R messaging: "Trump, Trump, Trump".
What people hear: "Trump, Trump, Trump, Trump, Trump, Trump".
Next time talk about your candidate, your plans, and say the word "change"about a billion times. It doesn't have to make sense or be true.
Democrat operational mistake Two
Democrats being shocked they had lower support in some of their core constituencies is a symptom of their mistake.
Identifying their core constituencies by race or gender was the mistake. I will give them identifying things like unions or other groups that you must join as a way to pack your message and measure effect. Groupings that you must join show more about what you think and what you actually do.