In primaries, we usually weed out the unworthies. In any election, there is too much at stake to let a Liberal/Progressive/Leftist/Socialist.....have an advantage.
You didn't get too good a look at the California election for Governor had you?
I'm curious -- common occurrances these days indeed have pitted, Liberal-Progressive Republicans vs. a Leftist-Socialist Democrats. In this scenario, tell me how "we" win?