Michele Bachmann has said she has a “titanium spine.” But does she have the facts right on this? Her infrastructure seems more like steel. After all, titanium can be flexible, but she is not. Metaphorically and physically, the Minnesota congresswoman is as rigid as rebar.

Bachmann’s tightly wound stage presence goes beyond the cool reserve you might expect from this descendant of Norwegians. She possesses a driving fierceness that borders on unnerving. Or maybe that’s just the fire in her eyes. In debates, she locks onto the moderator with a fixed stare, blue eyes fringed with heavy lashes. That smoky look adds a little drama to her responses, which otherwise march forth with ticktock assurance, relentlessly and without pause.

Steeliness defines her. There is no hesi­ta­tion. Her delivery is as predictable in tone and tempo as an automaton’s until the coda: the cheery smile with which she embellishes her applause lines.

“How will we have a pro-growth economy?” Bachmann demanded in a New Hampshire debate. “President Obama can’t tell that story.” Her eyes sparkled above a spreading grin. “His report card has a big failing grade on it.”

That winning smile is part of the Bachmann architecture, a brilliant and highly marketable structure in which an array of appealing details festoons steel beams of dispassionate, unyielding beliefs. Take her appearance, every aspect of which is polished and soothingly retro, from her pink lipstick and false eyelashes to her hair, whether in a lacquered updo or an equally unmovable blowout.

These are not Bachmann’s only vintage-Americana elements. She has dug further into the baby-boomer nostalgia closet for her ladylike suits. A crisp appearance is of such importance to her campaign that, according to the New Yorker, reporters are told not to distribute images of her in casual clothes.

But for the telegenic makeup, Bachmann could be auditioning for schoolmarm in chief. And therein lies the paradox. The congresswoman combines proper, endearing femininity with its flip side — the aggressive extremism that most of us associate with swaggering men. The tension in her presentation is compelling. How far can she take it?

One answer came in a CBS News debate last month. Declared the petite woman in a cocktail suit and pearls: “If I were president, I would be willing to use waterboarding.” She was the very picture of a Junior League luncheon organizer. Did she really say she’s okay with torture?

She did. And then she folded her hands and stood, as she always does, immobile behind her lectern, looking straight ahead. The candidate does not seek interaction in the debates. She shows little interest in what the others are saying. Her mind is already made up.

Clearly, Bachmann is selling chipper inflexibility. But even Margaret Thatcher, something of a soulmate in female conservative leadership, possessed a bit of physical grace and a touch of softness in her speaking style that indicated she was at least human, with a hint of an inclination to care.

Bachmann wants voters to believe her rigidity is a strength, but it is also her weakness. The office of president requires an ability to bend, to hear other views, to empathize with others’ experiences and beliefs. As approachable as she may look, Bachmann stands within a fortress, and the message is clear: Keep out.