Evangelicals are avid supporters of Israel and the Jewish people. That could be the reason for them calling her “The Jewish” candidate.
I live in NYC, 99 times out of a 100, if you hear a name even remotely like Bachman, you can bet the person is jewish.
Its kind of like the name bloomberg, or green, she has a pretty ethnic jewish name.
Sidenote: Funny story, former NY met and NY Yankee David Cone was often mistaken for being jewish, and used to get frequently (and still does) invites for jewish events and functions, its actually considered unusual and unique trivia for people to discover that he is not in fact jewish.