Here’s Princeton University Professor of History Sean Wilentz giving a series of three lectures at Harvard University on slavery and the US Constitution. This is in the Nathan I. Huggins Lecture Series.
You can see the lectures here.
This is really excellent, and I find it very persuasive. I think his critics need to see the series, because I don’t think they are responding to his actual position. They seem to me to be responding to their perceptions of his views–perceptions that are, in my opinion, inaccurate.