That's just plain weird. Since when is the "middle class" as a rule "Republican?" That mush in the middle cannot be labelled.
At least for the last half century, that has always been the case. The ultra-poor and the ultra-wealthy are Democrats. Working people, especially those with college-graduate-type professional occupations tend to be Republicans.
It is also true that the Democrats ultimate goal is to turn the US into a third-world country, with only two classes; the wealthy and the peasants. This is easy to see from all of their policies. You simply have to look past their PR/rhetoric, though. Because they are good at labeling things as other than they really are. For example; the Dems always want to tax the “Rich”, but the actual rich folks (like trust-fund Ted Kennedy) already have their wealth, and we don't have a wealth-tax (other than the estate tax, which the uber-wealthy manage to minimize). We have an income-tax, which hit hardest those who are successful, but still working and trying to accumulate wealth. In other words, the middle class.