"The South could never have won the Civil War," is a true statement, reflecting the various ways in which the Southern states attempted to fight a losing battle from the beginning. The economic dependency of the South on cotton on slavery was obvious, whereas the North had diversified and sufficiently. The advantage also lay with the North for reasons such as better communication and transportation, and even more soldiers.

The leadership in the North under Abraham Lincoln was far superior to the less savvy Jefferson Davis. It is also a fair argument to say that the just cause always overcomes, and morally, slavery was not just at all.
In the 1850's the North was more populous and urban, due to all the Irish and German immigrants that traveled to the states. By1860, 9 out of the 10 biggest cities were in the North. The North also had 70% of the railroads, and more telegraph lines to send messages instantly.

The North had a lot more industry also, with its 10,000 factories that brought in $1.5 billion dollars in goods compared to the South's 20,000 that brought in $155 million.(Source 1) The
South did, however, have more slaves and more cotton. This was not any sort of military advantage, and merely made it more obvious to the North how desperate the South was to keep its peculiar institution running.
Additionally, the first attack at Fort Sumter was poorly organized and was expected by the North.

Lincoln had wanted to attack, but waited so as to retain the sympathies of any Northern moderates. The South's attack played into what he wanted.
Once the war began, the military expertise of Ulysses S. Grant for the North made it an uphill battle for the South. His military skill alone was enough to give Robert E. Lee's forces in the South serious problem, but the Union army also greatly outnumbered the South's troops.

Though Lee would prove to be a worthy general, his strategic downfall at Gettysburg would begin the inevitable loss for the South. (Source 2)
In conclusion, it was obvious from the beginning of the Civil War that the South would not win the war. This having been said, Robert E. Lee was a fine general, but was simply without enough soldiers to lead a successful uprising. The economic superiority of the North was not a helpful factor for the North.

Finally, the leadership savvy of Abraham Lincoln was the kiss of death for the Southern cause. In history, the secession of the Southern states and the war following it will be seen as tragedies and mistakes. This blemish on American history could have been avoided has Southern leaders realized that all the bloodshed of the war was a doomed enterprise from the beginning. Henry Clay, the great compromise, would not have been happy with the failure of any bloodless compromise to be reached.