This is Bret Stephens’s first column.

When someone is honestly 55 percent right, that’s very good and there’s no use wrangling. And if someone is 60 percent right, it’s wonderful, it’s great luck, and let him thank God.

But what’s to be said about 75 percent right? Wise people say this is suspicious. Well, and what about 100 percent right? Whoever says he’s 100 percent right is a fanatic, a thug, and the worst kind of rascal. — An old Jew of Galicia

In the final stretch of last year’s presidential race, Hillary Clinton and her team thought they were, if not 100 percent right, then very close.

Right on the merits. Confident in their methods. Sure of their chances. When Bill Clinton suggested to his wife’s advisers that, considering Brexit, they might be underestimating the strength of the populist tide, the campaign manager, Robby Mook, had a bulletproof answer: The data run counter to your anecdotes.

That detail comes from “Shattered,” Jonathan Allen and Amie Parnes’s compulsively readable account of Clinton’s 2016 train wreck. Mook belonged to a new breed of political technologists with little time for retail campaigning and limitless faith in the power of models and algorithms to minimize uncertainty and all but predict the future.

“Mook and his ‘Moneyball’ approach to politics rankled the old order of political operatives and consultants because it made some of their work obsolete,” Allen and Parnes write about the campaign’s final days. “The memo that one Hillary adviser had sent months earlier warning that they should add three or four points to Trump’s poll position was a distant memory.”