I've been trying to sort this out in my mind for eight years, and now I think I've finally got it.
Why do Republicans win elections?
Republicans are more clearly focused on the attack and Democrats are more focused on their reaction to it. Democrats haven't built up their own identity independent of the Republican attack machine. They've allowed the Republicans to run the table and set the agenda.
Republicans are more clear about who their audience is and what those people think and care about. Democrats are trying to appeal to the humanity of all people, but people aren't listening with their humanity in mind. At least most are not. They're listening with their little mind.
On a related note, Americans have gotten more intellectually lazy and incurious in the past decade. Republicans have found it "a natural" to take advantage of that. Liberals...Democrats want people to be their best...to be like them...to think about things and consider the big picture. Republicans say, "I am like you and here's what that means."
Just some late night thoughts on a Friday night.