I wrote about the debate for Bloomberg Opinion.

Senator Kamala Harris, as a black female senator from the biggest state in our country, was always likely to be a strong contender. In the second of the first two Democratic debates, though, she also stood out as the coolest and toughest professional on the stage. Joe Biden has also been a top candidate, on paper, having served as vice president in an administration Democratic voters dearly miss. But his debate performance, while not deadly, is likely to deepen those voters’ worries that he is not up to the job of beating President Donald Trump in 2020.