The biggest, most consequential moment in all of the Democratic debates so far was Kamala Harris’s clash with Biden over busing in late July. The result? Harris doubled her polling for a short time before falling back down to Earth and then ultimately out of the race altogether.
Other than that? Elizabeth Warren rose steadily over several months and has now fallen back somewhat in the polls, but there’s no reason to think her performance in the debates has been a big factor in those changes. The professional debate critics at major media organizations have repeatedly pronounced Biden an inarticulate, doddering dud, even as he’s maintained his solid lead. Over and over again, Cory Booker has been called a rising star, the underdog who’s overdue for a breakout moment. But the moment never came, and he didn’t even make the debate stage this time. They’ve said similar things about Amy Klobuchar — and some said it again on Thursday. And it’s true, she had a good night. Just like she did the last time, and the time before that. For all the good it’ll do, which is not much. (She currently stands around 3 percent in the polls, which is 24 points behind Biden.)
The fact is that there isn’t much evidence that the debates have made any significant difference to the shape of the race. Which, again, doesn’t mean that those of us who are paid to watch, or who do so out of sheer, inexplicable perversity, weren’t rewarded on Thursday night for our devotion to political competition.