Democrats and Middle America: What's the Real Problem?

Why is it so hard for Democrats to get votes from people whose economic interests should lead them to support the party? Is Hillary Clinton right to identify the root cause as the party's lack of credibility as a protector of national security and to seek a remedy in a hawkish approach to foreign policy? Is the problem primarily cultural, a feeling that liberal elites are hostile to the values and religious beliefs of ordinary Americans? Or is it simply that Democrats have pursued an economic agenda of free trade and deregulation—against the interests of working people—leaving the party defenseless in the face of Republican demagoguery on whatever issue comes to hand?