With the arrival of the pope, our spirits lift.

With the departure of Scott Walker, they plummet.

There’s so much we’ll never know, such as how far he was willing to take his single issue. For Walker it was unions at dawn, unions at dusk, unions in his dreams. Having hobbled them in Wisconsin, he vowed to cripple them nationally, and who’s to say it would have stopped there? I feel certain that he was mere weeks away from a big speech advocating the deployment of ground troops to stamp out collective bargaining among the Sherpas in Nepal.

I feel certain, too, that his best gaffes were still to come, though he gave us several gems. In an era lacking visionary leadership, he envisioned a great wall along our northern border to keep out the tides of Canadians fleeing the tyranny of free health insurance. And we learned that years back, he mangled an intended “mazel tov” in a letter to a Jewish constituent, instead writing: “Thank you again and Molotov.”I miss him already. And I wonder: Was it his shallowness that undid him? Just how little learning will Republican voters abide in a candidate? Did he test the limit?One of his former aides, Liz Mair, suggested as much, firing off tweets on Monday about his errors, including “not educating himself fast enough” on national and world affairs.

Walker evaded foreign policy questions, apparently petrified of being tripped up. He bungled domestic policy questions, seemingly unable to cling to a sturdy position.

But whether that doomed him is impossible to say in a Republican primary season with mixed messages about the party’s appetite for ignorance, at once prodigious and inconsistent.

Donald Trump has prospered, and he’s utterly unapologetic about all of the matters that he hasn’t taken the trouble to bone up on and all of the experts whom he hasn’t bothered to consult.

When NBC’s Chuck Todd asked him where he gets his military advice, he said: “I watch the shows.” He presumably meant “Meet the Press” and “Face the Nation,” though I don’t think we can rule out “Survivor” or “Game of Thrones.”Time and again, Trump pledges to amass the proper information just before he needs it . no point in doing so now, before he finds out if he’s hired . and he predicts that he’ll shame everyone then with his abracadabra erudition. He’s a procrastinating college freshman planning an all-nighter before the final exam.

But here comes Carly Fiorina, and her brand is aced-it-already and know-it-all. I’ve seen this firsthand.

For a magazine story in 2010, I followed her around and interviewed her over several days. Someone would mention a flower; she’d rattle off a factoid about it. I’d ask her about a foreign language that she’d studied; she’d make clear that she’d dabbled in two others as well. Her husband would tell a story; she’d rush to correct him and fill in the details.

Her fresh bounce in the polls reflects a debate performance last week that was all about policy fluency, and Marco Rubio, who flaunted similar chops that night, also seemed to benefit from his show of smarts.

So do Republicans want finesse or fire? A cool intellect or a hothead?Walker was no doubt as confused about this as he is about so much else, and no wonder. Well beyond the Republican primary and the Republican Party, we’ve exhibited a curious habit in this country of forgiving intellectual blind spots and refashioning a contempt for schooling as an embrace of common sense.

A whole subgenre of nonfiction is devoted to this. Don’t sweat the brain work, because there’s “Emotional Intelligence.” Don’t think, “Blink.” Obtuseness in a leader can be redeemed by “The Wisdom of Crowds.”I’m being somewhat loose in my description of those books. And I’m not rejecting the importance of instinct.

But I’m weary and wary of politicians whose ambitions precede and eclipse any serious, necessary preparation for the office they seek. Walker is a perfect example.

I kept hearing and reading . after he’d obviously decided to run for president . that he was being briefed by an emergency crew of wonks. Shouldn’t that have happened first? Shouldn’t he have been paying attention all along, out of a genuine interest in this sort of material rather than a pragmatic one?He wasn’t, and so this candidate . who had begun gaming out his political future all the way back in college, where he gave his classes short shrift . took an international trip during which he refused to discuss international relations, oddly claiming that it wouldn’t be polite.

Etiquette prevailed.

He didn’t.

Molotov, Governor Walker.