The problem is that I've never heard of fivethirtyeight.com before reading your comment. (It may be well-known, and trusted, in your country). So all I see is an appeal to a site on the Internet to justify an assertion that Fox is reliable.
This is the same problem that people had with criticalstudies.org. It's another site on the net making claims. How do you verify that they are trustworthy?
The first thing that springs to mind with a name made of a series of numbers is a Chinese cyber-propaganda battalion. I highly doubt that is who is really behind it.