According to the author, why didn't James Madison help to end slavery in the biography, The Great Little Madison?

Fritz develops the theme of union throughout The Great Little Madison and uses it to offer some insight into why Madison sometimes contradicted his own ideals: "James might be a Virginian, but first and foremost he was and always would be an American pushing for a genuine union of the states."

This idea of holding together the union of the states as his first priority may explain why he did not push for the end to slavery in the United States; some slave states might have rebelled (as they would in 1861 over anti-slavery during the term of President Abraham Lincoln).