If the South never seceeded

[Dr. Cynic]

Well, those who speak of Douglas, it's doubtful that he would have tolerated the south any more than Lincoln. Douglas was, after all, the Little Giant, and he would have probably delayed, but not stopped sucession.
He would more than likely have done the same thing as Lincoln did.

But, of the men listed, Davis would have had a good chance at the Presidency, as Breckinridge did in 1860.

As for Robert E. Lee, he probably would have gone on to become a more celebrated General than he is today. Even a slightly different descision on his part would have dramatically altered history. If he had taken the Major Generalcy, and once again been at the side of Winfield Scott, it's doubtful that we'd hear much of Ulysses Grant, and Lee more than likely could have become President.

[Dr. Cynic]

According to dual Lee/Grant biographer, Gene Smith, Lee only fought for the South because of the involvement of his beloved Virginia.

When Scott heard, he told Lee "You have made the greatest mistake of your life."