Perhaps the more serious may be shifts among millennials, a generation that, for the most part, stands most in danger of proleterianization. Once solidly pro-Democratic, this generation has become increasingly alienated as the economy has failed to produce notable gains. In states across the country, the Republican share of millennial votes grew considerably. According to exit polls, their deficit with voters under 30 has shrunk to 13%. The Republicans actually won among white voters under 30, 53% to 44%, even as they lost 30- to 44-year-olds, 58 to 40. If these trends hold, the generation gap that many Democrats saw as their long-term political meal ticket may prove somewhat less compelling.

If they are losing the middle and working classes, and even some millennials, what are the Democrats left with? They did best in states like California and New York, where there is a high concentration of progressive post-graduates and non-whites, and where many of the sectors benefiting most from the recovery have thrived, notably tech, financial services, and high-end real estate.

Yet these areas of strength could also prove a problem for the Democrats. A party increasingly dominated by progressives in New York, Los Angeles, the Bay Area and Seattle may embrace the liberal social and environmental agenda that captivates party’s loyalists but is less appealing to the middle class. Unless the Democrats develop a compelling economic policy that promises better things for the majority, they may find their core constituencies too narrow to prevent the Republicans from enjoying an unexpected, albeit largely undeserved, resurgence.