A number of factors gave the South some chance to win the Civil War. But there are several caveats.
The South was fighting a "defensive" war on their home ground. But key to their defense were "border" states like Kentucky and Missouri. When these states tilted north, the South was "outflanked." Had they joined the South, it would have had natural defensive boundaries on the Ohio and Mississippi Rivers.
The South was more like Europe than the North, and European powers such as England and France were initially pro South. As it turned out, they had other worries such as Germany and Russia, and paid less and less attention to events on the other side of the "pond."
Many of the better American generals were Southern. These included the Albert Sidney and Joseph E. Johnston, Thomas J. "Stonewall" Jackson, James Longstreet, Jeb Stuart, and above all, Robert E. Lee. This advantage declined as the war progressed, with Albert Johnston, "Stonewall" Jackson, and Jeb Stuart getting killed, James Longstreet wounded and out of action, and northern generals like U.S. Grant and William T. Sherman getting better.
The South's best chance to win the war was early in the war, perhaps by striking a "knockout" blow for psychological reasons such as capturing Washington D.C., or some other major northern city, probably relinquishing it and attacking another target if the Union army tried to intervene. Only "a string of" (not a single) victory might have won them the war. It did not have the industrial and manpower resources to fight a long war, and the North did. So the longer the war, the lesser the South's chances.