The credit crunch of 2008. Stagnant wages. Growing wealth inequality. Outsourcing of blue- and white-collar jobs. Collapsing road and bridge infrastructure. Inadequate public transportation, or at least the perception of inadequate public transportation.
I think you could find a number of reasons. Many of them are not new phenomena, but wars and other calamities may have overshadowed these issues in the past few cycles. Also, many of the problems have grown worse. Consider this graphical representation from US census data:
People generally swing left after periods of lost economy, or of economic stagnation, and for the middle classes, that's exactly the reality.
