Arpaio's pardon will be over three years old in November of 2020. I think other national issues will carry much more weight in Arizona and elsewhere by the time the next presidential election rolls around.
bolded is the problem with the argument. The thread is referring to AZ not a national level. This post describes exactly why Arpaio won't be a national issue, because there are those who are not from here and do not understand the pain and suffering. With that said yes, All politics Is local, Dems should use this local issue to carry AZ in 2018 and 2020.
This will not cause the Dems to win PA, but it could cause them to win AZ.