On all sides, memorialists are saying he elevated the concept of original intent into constitutional law. Since nobody else will say it, let me state the obvious: hogwash.
The original intent of the Framers was to preserve chattel slavery. A Roman Catholic scholar -- but a very different kind of Catholic from the ritualist Scalia -- Garry Wills, says this:
"One of the effects of this line of argument [that the slave power conspired against freedom] was to continue the marginalizing of abolitionists, an effort at which the South was very effective. William Lloyd Garrison was the Ur-conspiratorialist in this view. He thought even the Constitution a plot against freedom ('a covenant with death'). He went beyond criticism of the open concessions to southern demands -- on the three-fifths clause, the slave trade, and fugitive slaves -- and found a pro-slavery slant throughout the document. A claim that this was the conscious aim of the framers cannot be sustained.
But Paul Finkelman shows that the South did find ways to use many clauses of the Constitution, and many interpretations of it, to protect their slave property. The concept of 'state sovereignty' was just one of these tools. For southerners 'state's rights' meant first and foremost the right to declare that their slaveholding was no one else's business. Other constitutional conveniences afforded them included the bans on taxing exports or interstate taxes, which favored the products of slave labor. Similarly, the guarantee of states against domestic insurrection, and the use of the militia for that purpose, put the federal government on the slave owners' side if their property should rebel. The 'full faith and credit' clause made other states recognize all the South's legal provisions for slavery. And so on."("Negro President": Jefferson and the Slave Power, pp. 10-11)