"It has been postulated among some historians that straggling during the 1862 Maryland campaign was so pervasive that it made serious inroads in the numbers of Southern "feet on the ground" and thus contributed to the failure of Lee's campaign."

I just finished rereading Stackpoles book "From Cedar Mountain to Antietum" and he alludes to just such a possibility, given the distances Lee and Jackson marched, and the battles fought. The Union Armies were not much better off. But thier commanders seemed to be the problem with them rather than the distance involved.