One Cause of Civil War
Delegates to the Constitutional Convention were instructed to revise the Articles of Confederation, but because of its two principal defects exposed during conduct of the Revolutionary War — no powers to tax states or regulate navigation and interstate commerce — they quickly decided it had to be replaced, not repaired.
"The spirit behind [the Constitution] was the spirit of compromise, seemingly no very noble flag to rally round. Compromise can be an ugly word, signifying a pact with the devil, a chipping off of the best to suit the worst.
Yet in the Convention the spirit of compromise reigned in grace and glory; as Washington presided, it sat on his shoulder like the dove." 
Southern delegates realized that giving Congress power over the omissions in the Articles would give large, anti-slave states power to regulate the Southern slave trade!
In the end, a compromise was reached. It was "settled by a bargain."
Congress could regulate navigation and interstate commerce and collect taxes. In return, slaves could continue to be imported until 1808, navigation acts could be passed only by two-thirds vote of both houses, and the "federal ratio" would be used for purposes of representation and taxes e.g., five slaves would count as three free whites.
"Without disrupting the Convention and destroying the union, they could do no more." Hamilton said, "Without the federal ratio no union could possibly have been formed."
They were not there to legislate but to craft an agreement among states as they were.
The Declaration of Independence (1776) and the Articles of the Confederation (1781) were issued by the "Free and Independent STATES."
By contrast, the Constitution begins, "We the PEOPLE."
Bowen used the metaphor of marriage in which a confederation is like cohabitating and a union is like a marriage, the former ending when the partners fall out of lust and the latter enduring till death do us part.
John Adams used an ancient Greek metaphor of the sheepdog to illustrate the problem of establishing a government strong enough to act but not strong enough to turn into tyranny. A sheepdog has to be strong enough to protect the flock from external threats but controlled enough to not leave the flock vulnerable to his depredations.
Article II of the Articles of Confederation read, "Each state retains its sovereignty, freedom, and independence, and every power, jurisdiction, and right, which is not by this confederation EXPRESSLY delegated to the U.S., in Congress assembled."
Significantly, the 10th amendment to the Federal Constitution later defined the Federal system somewhat differently by leaving out the word "expressly," thereby permitting the federal government certain implied powers of far-ranging consequence." 
Page 2 of 3 - Nullification
Jefferson's "exotic" vision of state's rights before he became president was as a compact of sovereign states, any one of which could substitute its own views on constitutional questions for those of Congress.
Chief Justice John Marshall of SCOTUS countered that national sovereignty is vested in the people of the U.S. as a whole, not the people of each individual state.
State legislatures that disagreed with Supreme Court decisions should be free to defy them e.g., the theory of "nullification."
This vision would thwart the effort by the framers of the Constitution to create a system of national laws that all citizens were obliged to follow, whether they agreed with them or not. 
The nullification doctrine later bore toxic fruit in Jackson's presidency.
After gold was discovered on Cherokee land, the state of Georgia passed laws seizing their territory. The tribe sued. SCOTUS ruled in favor of the tribe, but Jackson defied their decision saying, "John Marshall has made his decision, now let him enforce it."
The state of Georgia simply ignored the decision, setting an ominous precedent. 
Lincoln began political life as a member of the Whig political party, which held the "Whig straddle" of pro-union and pro-slavery positions.
It was a political middle ground that was basically untenable and gradually disappeared with Lincoln emerging as the leader of the pro-Union, anti-slavery faction that morphed into the new Republican party.
By 1860, the parties were polarized with mutually exclusive policy positions and no moderates in the middle available to bring about compromises with ballots — leaving the only solution bullets.
Lincoln was elected in November 1860, and by February 1861, six Southern states had seceded and formed the Confederate States of America (CSA) with Jefferson Davis as its president.
Had they been permitted to go, it would have validated their view of the union as a voluntary association and, consequently, ended the U.S.A.
By April 12, when CSA militia captured Fort Sumpter, five more states had joined the CSA.
Secession, the ultimate nullification, was based on Jefferson's interpretation of the Constitution as a compact among sovereign states, not a union of the people.
The names chosen for the war that followed reflected their contrasting interpretations e.g., to the South, the Civil War was the War of Northern Aggression.
Lincoln was inaugurated March 4, 1861, and in his first inaugural address he took an oath to "preserve, protect, and defend" the Union.
Then, the connotation of "union" was an instrument of the sovereign states.
By war's end, however, Lincoln used "nation," which implied an instrument of the people. The purpose of the war was not to end slavery but to keep the nation intact.
Page 3 of 3 - Confederate soldiers at Gettysburg indicate that they were not fighting for slavery but for states' rights to protect their culture and for their families.
 Bowen, Catherine, 'Miracle at Philadelphia,' NY: Little Brown, 1966, Ch.XVI.
 Framing the Federal Constitution, National Park Service, 1986, Handbook 103.
 Rosen, Jeffrey, 'The Supreme Court,' NY: Times Books, 2006. 50-1;62-3;66-67;80.