How is it in our best interest to primary him?
Regardless of what you think about the viability of running progressive populists in predominantly white-working class areas, what progressive populist is going to be willing to shill for the coal lobby as part of their main platform? The reality is that West Virginia has offered little signals that it wishes to diversify its economy despite the decades long decline of the coal industry, and until they do demonstrate willingness to try new things, they won't support any candidate that's anti-coal.
Primary him with somebody more progressive and watch him get replaced with a staunch, party line Republican. Congratulations on voting out of office somebody that still votes over 60% of the time on Democratic agenda items and replacing him with somebody that votes for Democratic items 0% of the time. You really showed those DINO's how it's done!
Completely agree with everything you said, including the bolded, but it is kind of funny that the only Republican WV Senator in the past like 60 years (the current one) is pretty moderate.