This year’s newly reset presidential race features a former president running against a sitting vice president, but don’t expect to hear either candidate dwell on their existing power. In Time magazine last year, the political scientist Lee Drutman laid out some reasons incumbency is no longer the edge it once was: “Unrelenting media scrutiny; a bruising political environment; pervasive anti-politician bias; and above all, a spiraling hyper-partisan doom loop of animosity and demonization that imposes a harsh starting ceiling on any president’s approval.” (One sign of the calcification of American politics is that Harris’s ascendance to the top of the Democratic ticket was simultaneously shocking and insufficient to move polls by more than a couple of points.)