It's been this way for a long time - Obama is just making it official.

Mickey Kaus argues that Obama is throwing working class whites under the bus of a new Democrat coalition:

In the aftermath of Obama’s gay marriage flip, pundits seem to have concluded that Obama’s Democratic party has indeed given up on white working class voters. They’ve been dropped from the winning coalition, which is now composed of three main groups: “young people, college-educated whites (especially women), and minorities,,” according to Ron Brownstein.”

And:

3. Weren’t Democrats supposed to be the party of Everyman? If you went to work and obeyed the rules, Dems would “make work pay”–plus give you unemployment compensation and Social Security and medical care in old age. White male workers are sort of the indivisible denominator in American politics–they have no special economic leverage, and no race- or gender-based claim to special privileges. They’re naked as far as favoritism goes, and thus (not unlike Marx’s proleteriat) are the representatives of universal privileges (such as Social Security). The new Obama coalition threatens to abandon this universality, becoming instead the party of non-universal skills, ethnic and gender identities–of special pleaders, victims and causists. Not of citizens.

Let's get real. The Democrats stopped appealing to citizens qua citizens, as opposed to balkanized interest groups, sometime in the 70s.