The mistake about Paul Ryan, the one that both friends and foes made over the years between his Obama-era ascent and his just-announced departure from the House speakership, was to imagine him as a potential protagonist for our politics, a lead actor in the drama of conservatism, a visionary or a villain poised to put his stamp upon the era.

This Ryan-of-the-imagination existed among conservatives who portrayed his budgetary blueprints as the G.O.P.’s answer to the New Deal, among centrist deficit hawks who looked to him to hash out their pined-for grand bargain, and among liberals for whom Ryan was the most sinister of far-right operators, part fanatic and part huckster — a Lyle Lanley with “Atlas Shrugged” in his back pocket, playing everyone for suckers while he marched the country into a libertarian dystopia.

It existed among the donors who wanted him to run for president, the pundits who encouraged Mitt Romney to choose him as a running mate, the big names who pressured him into the speakership. And it existed among anti-Trump conservatives, finally, who looked to Ryan to be the Republican of principle standing athwart Trumpism yelling stop.

But the real Ryan was never suited for these roles. He was miscast as a visionary when he was fundamentally a party man — a diligent and policy-oriented champion for whatever the institutional G.O.P. appeared to want, a pilot who ultimately let the party choose the vessel’s course. And because the institutional G.O.P. during his years was like a bayou airboat with a fire in its propeller and several alligators wrestling midship, an unhappy end for his career was all-but-foreordained.