This makes the most sense as a "who to vote for" in the [private] primary systems we use to determine who to vote for in our very openly rigged two party system. We/the "two parties" purposely drag the parties to extremes by having their primaries in certain states and candidates are driven to court extremes and we pretend that's good as many valid candidates are "weeded out" that way. (Again, it's a private system, So even non-centrist candidates, famously Bernie, can just be ignored as the party chooses who they want)