But, but, but: By the time Inauguration Day rolls around in 2021, it will be “too late to turn back to the clock” on the most daunting challenges the U.S. faces, says Richard Haass, President of the Council on Foreign Relations.

He says “elements of Trumpism,” possibly on trade, could carry over into the next administration. In any case, he says, the next president will be “constrained by the fact that the world has moved on.”

“Even if the next American president sends reassuring signals, rejoins this or that, there’s still now an element of doubt about U.S. policy. There’s no longer the presumption of continuity that there was, and there’s a sense in the world that if it happened once it can happen again.”