Well I think they
are losing the white working class voter. Remember about 2 years ago there was an op-ed in the NY Slimes basically urging the Democrats to forget about this part of their coalition and move on with "the future"?
My parents were the first generation from either of their families to be Republicans. My grandparents were old school Democrats, and for a long time people just like them were the core constituency of the Democratic Party. They were socially conservative and pro-American. There's no way they would see any aspect of themselves reflected in the modern Democratic Party.
Their loss is not necessarily the Republicans' gain, though. That's not a bad thing. It may hasten the rise of something new.
ETA: Here is the NYT editorial --
http://campaignstops.blogs.nytimes.com/2011/11/27/the-future-of-the-obama-coalition