This will be the ninth Democratic debate but the first featuring former Mayor Michael R. Bloomberg, and he is bound to face an avalanche of attacks from his rivals. Mr. Bloomberg’s rise in recent polls has coincided with the decline of Joseph R. Biden Jr., who needs a big debate performance to recover from stinging losses in Iowa and New Hampshire.
Senator Bernie Sanders, who appears in strong shape heading into Nevada’s caucuses on Saturday, simply needs to continue avoiding the scrutiny that some rivals have received in past debates. Tonight is also a chance for Senator Elizabeth Warren to regain her footing pre-Super Tuesday and for Pete Buttigieg to show he can speak to the concerns of a racially diverse electorate. The surge of Senator Amy Klobuchar in New Hampshire after one strong debate showed just how much these television spectacles can matter.