I dunno, I suspect women and minorities will eventually outnumber old white men.
It's a general expression. Just like how the GOP is (deservedly) gaining the reputation of being a party of nothing but old white men, the Democrats are (also deservedly) gaining the reputation of being a party of single women and minorities. Both are equally stupid to allow which for some reason both are perfectly capable of accepting for some dumb reason.
First of all, even though the white share of the vote is decreasing, it still doesn't change the fact that they still make up 70% of the electorate. And with the way the Democrats have been losing the white vote, it is really biting them in the ass when it comes to Congressional, gubernatorial, and statehouse elections. Mary Landrieu just lost in a landslide because her performance with whites is as embarrassing as the GOP's performance is among blacks. When whites still form the overwhelming majority of voters, it's a poor strategy to just brush them off.
Second, I say single women. Single women are clearly a Democratic bloc, but married women are a swing bloc. For some reason, Democrats like to lump all women together and think that they all share the same values when the reality is that the interests of single and married women diverge quite a bit. Married women aren't going to be as concerned about social issues like abortion the way single women are. The Democrats myopic focus on social issues in 2014 is a reason why the GOP won female voters in states like Kentucky or why the Democratic edge among women in states like Colorado, Iowa, and North Carolina were unable to overcome the MASSIVE deficit among men.
And finally, by relying far too much on minorities, the Democrats will not have a Congressional majority for a long time. Minorities so far, are still a completely unreliable voting bloc as opposed to other demographics like older voters, whites, women, etc.
Basically what I'm trying to say is that both parties need to actually try to be parties that have wide appeal, not what their current strategies are doing. With Republicans, they're alienating minorities (a demographic that is showing rapid increases) and women (who make up half of the electorate). And Democrats are alienating whites (who still form a big majority of the vote) and men (who also make up half of the electorate). The GOP's alienation is costing them the White House while the Democrat's alienation is costing them Congress, governorships, and state legislatures.