The Republicans tend to be socially conservative and economically libertarian.
The Democrats tend to be socially and economically liberal, in the American sense of the word.
You could include that certain demographics vote Democratic due to paranoia about the demographic that is perceived as Republican (White Protestant American - often rural). Meaning, if ever a politician came along that would want to send ethnics back to somewhere, and disenfrancise them from their citizenship, the perception is that a Republican (White Protestant America) would be the demographic and party that the politician came from. I read this some time ago; not my own thinking. If you remember there was a proposal to to make the United States officially a Christian country. It never passed, but that kind of gratuitous disenfranchisement stays in the minds of many.
The author gave examples of Indian Americans (from India) and American Jews as successful demographics that should have become staunch Republicans, but the concern about one day being disenfranchised, since they are either neither white or Christian supposedly is why they remain predominanctly Democratic.