Here is a thoughtful essay by Josh Marshall at TalkingPointsMemo.com by someone who was in a graduate program in history and then decided to become a popular writer. Some relevant excerpts:
…At one point in our conversation, he laid it on the line. “You need to decide whether you’ll be satisfied with writing for an audience of two or maybe three hundred people.”
Clearly, the correct answer to this was “yes.” And as Wood said it, then and now I have the sense he thought posing it in this way would get me back on track with a focus on the scholarly community we were a part of. But hearing it so starkly, in my mind my response was something more like, “Holy Crap, no way! That’s definitely nowhere near enough people. And worse yet, I know some of those people. And I definitely don’t want to write for them.”…
…For my part, for a while I figured I’d be one of those professors who professors and also writes magazine articles and columns. But eventually I realized that would mean I would end up mediocre at both. So I scrapped that idea and committed myself to making a career as a writer. After various false starts I was blessed, through a totally fortuitous set of circumstances, to be taken under the wing of the novelist and journalist James Carroll who among other things helped me land my first job in journalism. That was in 1998. The volume of work forced me to set the dissertation aside but kept myself enrolled for the next four years before finally carving out time in 2002 and 2003 to finish it and get the degree.