Duncan is partially correct; had it been possible for the previous compromises to continue in relation to the admittance of the states on the basis of free and non-free then the war either would have been long delayed or never have taken place. mechanisation of cotton production would have effectively seen slavery die out anyway. it was the unwillingness of the North to change constitutional conditions for state entry that ultimately led to the war. combined with a fear that the industrial strength of the North, already quite pronounced and shortly to become overywhelmingly dominant in the world, made an attempt at secession an increasingly now or never alternative- even 10 years on would have made a big difference in terms of population and economic power. eventually the south was swamped in a war of attrition.
slavery was the major difference between the states; it was slavery that retarded southern economic progress and caused the constitutional crisis. the election of Lincoln was the spark to a volatile situation. while publicly stating he had no intention of legislating an abolition of slavery, as Duncan himself has pointed out in a previous thread, there was no guarantee for the south that he would keep his word when in office.