julie. joe biden is pretty old school, so actually believe, to some extent, that he didn't want the endorsement. it's a long-standing tradition the democratic primaries for elected officials and people in a position of power to not endorse any primary, and give everyone a fair shake. so i would like to think that is what's going on here. >> julie: the question now is, does biden have the endurance or outlast his competitors? he still leads nationally. at one point, elizabeth warren was nipping at his heels. now pete buttigieg. a former obama advisor, david axelrod, here he is discussing joe biden's performance in the debates, and i will have you react. >> i wouldn't say he's a house of fire on any of the debates eventually. and yet he kind of bumps along, kind of mr. magooing has a way through this. [laughter] you keep worrying he's going to hit a wall. but he's moving forward.