Legs.

A campaign needs them. A pantsuit hides them. Might Hillary Clinton be sashaying through a swath of cheering delegates, a hangdog Barack Obama tagging behind, if only she never packed that first, fatal slacks-and-jacket ensemble?

In other words, if only Yves Saint Laurent hadn’t come along and changed the way powerful women dress?

After all, it was Saint Laurent, who died on Sunday, who first poured females into pants. Until he sprang onto the fashion scene in the late 1950s, the only women who dared wear trousers were the ones riding horses, planting bulbs, or busy being Marlene Dietrich.

Marlene wore pants and a top hat and wrapped men around her little finger — even if she was more interested in women. Voracious, German, Angelina without the baby bump, she was supposedly Saint Laurent’s inspiration.

And you wonder why Hillary’s stump outfit makes men cross their legs.

Saint Laurent started out by taking the epitome of male elegance and power, the tuxedo, and bestowing it on the weaker sex. Weaker no more. But then, like God fashioning Adam and thinking, “Hmm. This is a good idea, but I’d like to take it further,” he went on to create something familiar yet utterly new: le ready-to-wear pantsuit.

In one fell swoop, women were now wearing the you-know-whats. Welcome to the sixties.

That’s the era when Mrs. Clinton came of age, and for a lot of women who remember those days (if only faintly, because we’re way younger), the pantsuit represented more than just another outfit option. It represented equality.

Until I was in third grade, girls at my public school were required to wear skirts or dresses. In Chicago. In the winter. Fashion historian Nancy Deihl recalls that as late as 1971, when she was in sixth grade, “I got sent home for wearing pants under my dress because it was really cold.”

To us, the personal was pant-litical. Until we got to wear pants, we were second-class citizens, with goosebumps. Someone in power (was it you, Principal McAvoy?) insisted on seeing our little female legs. That’s why, to this day, the pantsuit equals something we love: feminism. But to a lot of others, the pantsuit represents something they loathe.

Feminism.

Of course, they’d never admit it, but that’s what’s going on. The pantsuit is, if nothing else, a Rorschach test. The ones who find it “ugly” or “unappealing,” have all sorts of totally contradictory reasons why. It’s too dowdy. Too aggressive. It hides too much.

“Have you ever seen Sarah Jessica Parker in one?” the co-author of, “The Art and Power of Being A Lady,” Dini von Mueffling, asked. To her, the pantsuit is what women wear when they don’t want to shine — pathos on parade.

But for others, it’s more nefarious — “Camouflage,” as one blogger asserted. He assumes Mrs. Clinton wears her pantsuits to hide her chunky legs. In fact, mention, “Hillary” and “pantsuit” and there is so much talk about her legs, she might as well be campaigning in hot pants.

Still others think she’s wearing the suits to blend in with the men running for president. Like that’s really likely: “I’m voting for the guy who’s married to Bill. Wha — she’s a woman?”

“The concern with pants is really deeply embedded in our society,” a professor at SUNY Cortland, Kathleen Lawrence, said. When people ponder Mrs. Clinton’s pantsuit penchant (and they do), “I think they see it as her rejection of the alternative” — a skirt or dress — Ms. Lawrence said. That way they end up thinking she’s not only ideologically attached to the pants thing, she’s completely inflexible, too.

That inflexibility (like most inflexibility) is what ended up making Mrs. Clinton the butt of so many jokes. Google “pantsuit” and “Clinton” and you get 376,000 hits — about half of them from David Letterman.

When she was riding high last summer, Mrs. Clinton went on his show and declared, ha ha, Campaign Promise #1: “One more pantsuit joke and Letterman disappears.”

But just a few days ago she was back, humbly offering the Top Ten Things she loves about America. Number 8: “Thanks to the Internet, I can order new pantsuits 24/7 — there’s your pantsuit joke, Dave. Are you happy now?”

Of course he is. He’s got her defining herself on his terms, as a lady bent on making herself look ridiculous. “To raise money, Hillary entered a wet pantsuit competition,” he chuckled the other day.

To women — and men — who appreciate the freedom Saint Laurent bequeathed us, the Hillary-pantsuit debate is a reminder that women may wear pants today, but plain old chauvinism still has legs.

lskenazy@yahoo.com