Nothing stops him or slows him or sours him, at least not for long. Nothing is beneath him, because he’s as unabashedly messy and slick as the operators all around him. He doesn’t recoil at the rough and tumble, or feel belittled and diminished by it. He relishes it. Throw a punch at him and he throws one at you. Impeach him and he bounces back.

It’s that very gameness that fueled his undeniable successes as a president, and that’s worth keeping in mind when the midterms end and we turn our attention more fully to the 2016 presidential race. Who in the emerging field of contenders has his level of enthusiasm, his degree of stamina, his intensity of engagement?

Neither of the two presidents who followed him do, and that absent fire explains many of their shortcomings in office. Both George W. Bush and Barack Obama felt put out by what they had to do to get there. Neither masked his sense of being better than the ugly process he was lashed to.

Bush was always craving distance from the stink and muck of the Potomac, and routinely averted his gaze: from the truth of Iraq, from the wrath of Katrina. In a different way, Obama also pulls away, accepting stalemates and defeats, not wanting to get too dirty, not breaking too much of a sweat. “The audacity of mope,” his countenance has been called.

It comes into sharper, more troubling focus with each passing season and each new book, including Leon Panetta’s, “Worthy Fights,” which was published last week. The reservations expressed by Panetta, who served under Obama as both C.I.A director and defense secretary, seconded those articulated by so many other Democrats.