A new book ponders that question, and answers in the affirmative:
I think, however, that the question of whether the South could have “won the Civil War” is really two different questions:
1. Could the South have achieved a complete and decisive military victory over the North?
2. Could the South have won its independence from the North?
In my opinion, the answer to Question No. 1 is a definite NO, it could not—the North was simply too much of an economic and industrial powerhouse, with a much more extensive and effective supply and transportation infrastructure, and a much more extensive pool of military-age men.
The answer to Question No. 2, however, is a definite YES, because the South didn’t need decisive military victory to gain independence—it only needed to convince a majority of Northern voters that continuing the war was a bad idea, and nearly did so in spite of the inadequate leadership of Jefferson Davis and the flawed strategy of Robert E. Lee!