Ann Romney gamely attempted to humanize her husband, Mitt, at the Republican National Convention on Tuesday night, and you could tell. She provided the sorts of details about their early marriage that politicians and their spouses often have on hand to make themselves seem relatable — their dining-room table was an ironing board, on which they ate a lot of tuna fish and pasta — right after explaining that Mitt’s father ran an auto company. And she kept insisting — too much — that Mitt makes her laugh.

In fact, Ann Romney’s most powerful lines were not about how Mitt Romney is just like the rest of us — but how he has shown himself to be very different. “No one,” she said definitively, “will work harder to make this country a better place in which to live.” She reminded the audience that her husband pursued business and law degrees at the same time. She described how Mitt started Bain Capital with a group of friends, succeeding in making millions hundreds of times over. And she ended her speech with a promise: “This man will not fail.”

Mitt Romney is a striver of uncommon commitment, for better and for worse. Since he began trying in 1994, he has lost more elections than he has won. In the process, he has taken nearly every side of some of the biggest issues of our time. He has pressed through not one but two presidential primary campaigns, subject to an increasingly brutal right wing punctuated by the rantings of Newt Gingrich and Rick Santorum. For all his torments, Job had it pretty good by comparison. And, yet, Mitt Romney has now claimed the GOP nomination for president.

The greatest argument for Mitt Romney is not that he’d be fun to get a beer with, or that he is rock-solid in his ideological principles. No one can really believe either. Mitt Romney’s most impressive and consistently manifest attribute is his inhuman work ethic. That also points to one of Mitt Romney’s greatest weaknesses — it remains utterly mysterious to what end, beyond his own advancement, he wants to apply all that talent and drive.

Read more on the Republican convention:

Ed Rogers: Ryan needs to stick to the economy

Eugene Robinson: Christie’s failed advertisement

Jamelle Bouie: The very narrow “we” in “we built it.”

Dana Milbank: The Ron Paul revolution