Short answer: a lot are liberals first and Jews second.
When looking at the PCIntern primitive, my good friend Jonathan, I'm guessing it's some sort of desperate, panick-stricken desire to "assimilate" themselves into what they perceive as the "mainstream" of American society.
Also, for generations, despite all the evidence to the contrary, they've been trained to believe that the Democrats are the smart party, the intellectual party, the hip party, the cool party, and that Republicans are just a bunch of stupid redneck
goyim.
They fail to see that actually they were "assimilated" a very long time ago, at least within the Republican party, where they've produced some of our finest talent and their feelings and opinions are important to the rest of us. They've been part of our crowd for ages, but only those within seem to realize this.
I've never seen a group of people more desperate to seek the liking and approval of others who hate them, despise them, so much, as those of Judaic derivation seeking inclusion inside the Democrat party.
