America has a long history of angry nativist political movements. Each succeeding immigrant group had to fight restrictions and prejudice from groups already here. It's shocking to read of the anti-Catholic actions of settled Protestants in the mid-19th century, and of the racist laws against the Chinese and Japanese at the end of that century. I've written before of the power of the revived Ku Klux Klan in the 1920s and further restrictions on immigration from Eastern and Southern Europe, especially Jews. Historian Richard Hofstadter wrote the classic analysis of the "paranoid style in American politics" in 1964.
So it should not be surprising that Donald Trump has rallied sizable support for his angry views about immigrants, women, and many others. Perhaps the most revealing story on who these aroused potential voters are is in this piece about a Frank Luntz focus group in the Weekly Standard. As other writers have noted, Trump supporters like his attitude, his style, more than they care about particular policies. That makes him dangerous to the U.S. political system.