My model of the parties is that the Democrats get their votes predominantly from the bottom of the income distribution and from the top of the the income distribution--from the inner cities and the toney suburbs. The two groups form a pincer against the middle class, which reacts by supporting the Republican Party.The low-income Democrats naturally don't contribute a lot to their party--don't even contribute to it at all, actually. So ironically the Democratic "party of the little guy" depends on larger donations from fewer, fatter cats than the Republican Party does.
This model agrees with the above quotation except that it suggests greater Democratic strength among those with more than a batchelor's degree.
You're correct about that.
I once saw a demographic breakdown of dems and Republicans. I don't remember where it was, but I do remember this great line. The democrats are the party of both the under educated and the over-educated. I think that is a perfect description.