Liberal Dems a dying breed?
The problem I have with data like this can be summed up in one question, "What is a Liberal?"
Do fewer Democrats self-identify as Liberal? I can believe that. But does that mean that, ideologically, fewer Democrats hold "Liberal" positions than they did 20 years ago? Or could it just be that "Liberal", as a label, has gotten such a bad rap that a lot of otherwise Liberal Dems just don't want to think of themselves as being Liberal?
Simplistic interpretations of this data suggest that Democrats need to become more Conservative in order to appeal to an electorate that is increasingly leaning right. But, if Dems are still Liberal in their hearts, even if they don't want to be called that in public, then adopting more conservative positions will just push them even further out of the Democratic camp.
The real problem for the Dems is not that the nation is leaning further to the right (I have serious doubts about that). It's that Dems are so afraid to self-identify with their traditional positions that a lot of Americans, both Democratic and not, are simply throwing up their hands and saying, "Screw you guys! At least the Republicans seem to know who they are."