Do visiting professors make for good PhD supervisor? I am currently thinking about pursuing a public policy PhD after my MA is completed. One of my top target schools employs a visiting professor who has been at that university for the past several years. The main reason I wanted that particular professor is that his previous background included posts at several very high-ranking positions within the US government that I feel like would be helpful to me throughout my doctoral education and with the potential dissertation. But I'm worried that as a visiting professor, he'd make for a poor choice as a supervisor due to him being "visiting" instead of a more permanent professor at the school (is it?).
Rules vary, but visiting professors should not be permitted to supervise PhD students because they are not employed for the duration of the supervision period.  So while they might be skilled supervisors, they are not suitable supervisors.