"[I]f a national referendum were held the day after Roe fell, there’s little doubt that early-term abortions would be protected and that later-term abortions would be restricted. But the U.S. Constitution doesn’t provide for government by referendum. Because of the intricacies of American federalism, and the polarization of American politics exacerbated by Roe itself, the moderate national consensus about abortion might not be reflected in law for years to come, and the political landscape could be transformed beyond recognition."