To be honest the Democratic Party shouldn't panic too much. Always learn from a defeat, but the demographics long term still favor them (50% of kids under 18 today are a "minority" group, one day soon that will be the US majority).
They won the popular vote by a large margin and Pennsylvania, Michigan, Wisconsin, are still traditionally blue states.
On important issues, the American people are leaning more liberal as time goes on. Gay marriage? Majority of Americans support it. Abortion rights? Majority of Americans support it. Taxing the mega-rich? Majority of Americans support this. More benefits for the middle class? Majority of Americans support this. Universal healthcare? Majority of Americans support that. Make it about the issues.
It's hard for any party to win 3 straight national elections, it gets harder every time, and Hilary Clinton simply wasn't a charismatic enough candidate with too much baggage.
Hate to say it, but Bernie would've won without much fuss as he would've locked Trump out of those Rust Belt states.
