Fleming tells us that “George Washington ignored protests from some Southerners and accepted both free and enslaved blacks in his army. In the final years of the war, one in every seven soldiers in his ranks was black.” Jefferson attacked the institution in an early draft of the Declaration. John Adams, in the Massachusetts constitution of 1779, inserted the plank “All men are born free and equal” which enabled judicial challenges to slavery in that state. Hamilton and Jay advocated manumission.
As Fleming reminds us, the “survival” of the new nation was the first priority of the Founding generation. To this end, the Founders compromised during the Constitutional Convention by allowing the slave trade to continue until 1808 and limited the voting power of the southern states by inserting the 3/5 clause. Fleming notes:
“In an emotional speech, 81-year-old Benjamin Franklin persuaded all but three of the delegates to ‘doubt a little of their infallibility’ and accept these and other compromises that made the Constitution a reality. That same year, Franklin accepted the presidency of the Pennsylvania Society for the Abolition of Slavery.”
Over all, Fleming gives a good review of the key points. I’d include the Northwest Ordinance’s elimination of slavery in federal territories recently relinquished by individual states including the largest slave owning state, Virginia. Indeed, statesmen from Virginia (Jefferson, Madison, Mason, Henry, etc.) made significant attempts to limit slavery in contradiction to their narrow interests.
I’d also remind the reader that the Constitution left many matters to the states in what was still viewed as primarily a federation. It prohibited the federal government from trampling the liberties of the people but as a federal structure it did not impose those prohibitions on state governance. We've particularly discuss this fact with regard to religion and established churches. Given the federal government's emphasis on matters of foreign relations (defense, trade, etc.), could one not say that, with the slated-elimination of the trans-Atlantic slave trade, that the federal government largely succeeded in the elimination of slavery in federal matters?
Overall, the efforts by leading statesmen to address the slavery issue is far greater than one might expect. Most often matters of principle are not high on the agenda without the powerful role of an aggrieved group whose narrow interest motivates the issue. For example, disestablishment of churches and respect for religious conscience may demand appeals to principle but those aggrieved (Baptists, etc.) needed to put pressure on those in power. In 1776 (or 1789) there was yet a Frederick Douglas to represent oppressed slaves. Opposition to slavery depended on the conscience of our lead statesmen. The world was just beginning to feel the pangs of discomfort over the institution of slavery. The awakening began here among our Founding Fathers.