The most disturbing professional debate I have listened to since the election was one between two young consultants who were arguing about running data-based campaigns versus message-driven campaigns. If the Clinton campaign did not offer everyone a lesson in a campaign without a message, then I can't imagine what would. The problem for Democrats is that not only do they not have a message, but many consultants may not even understand the meaning of the term message.
Some consultants seem to believe a message is just an issue statement, such as "I support equal pay for women" or "I support an increase in the minimum wage." There is one truism about campaigns that I think is an absolute - issues are only props to talk about the candidate as a person. Personal values and the voters' perceptions of the world are much more powerful than opinions about individual issues. If they weren't, candidates running on issues such as gun control or increasing education funding would be winning everywhere. Rather, people react emotionally to candidates as people.
In my book, The Four Pillars of Politics: Why Some Candidates Don't Win and Others Can't Lead, I point out that everything is filtered through four perceptions; fear, religiosity, consumerism, and narcissism. The candidate that reaches the voters at a gut level will win. Hillary Clinton's campaign did not connect with voters. Her basic slogan was even backwards; I'M WITH HER. The slogan and message for the campaign needed to be SHE'S WITH ME. In the voters' eyes, unless a candidate is with ME on an emotional and value driven level, voters have little reason to support them.