Overall, 88 percent of the contributions from car dealers went to Republican candidates and just 12 percent to Democratic candidates. By comparison, the list of dealers on Doug Ross's list (which I haven't vetted, but I assume is fine) gave 92 percent of their money to Republicans -- not really a significant difference.
There's no conspiracy here, folks -- just some bad math.
For all of you who don't know fivethirtyeight.com is a STATISTICAL website, not a political one. The guy who founded it is a statistical genius who used to work for major league baseball teams.