It lurks in the Produce Department, sneaky-silent, all tied up in a bunch, seemingly minding its own business even as it threatens to change the course of the 2008 presidential election. It is arugula. Some call it rocket, or roquette. It's a trendy salad ingredient, often viewed as a type of lettuce, though the government lists it as an herb.

Without question, it is the most politically explosive of the leafy greens.

At the loftiest levels of American politics, there are operatives who are eager to play the arugula card. When Barack Obama's campaign skewered John McCain for forgetting how many houses he owns, the McCain camp responded by dropping the a-word on him — twice.

First, McCain spokesman Brian Rogers sent out an e-mail describing Obama as "a guy who worries about the price of arugula." Later in the day, Rogers said in an interview, "In terms of who's an elitist, I think people have made a judgment that John McCain is not an arugula-eating, pointy-headed-professor type."

Obama's arugula problem dates to last summer, to an offhand remark in Iowa. He was saying that farmers could make good money planting specialty crops rather than just corn and soybeans. He asked his audience if anyone had seen the price of arugula lately at Whole Foods. Pundits howled: Arugula! Whole Foods! As if the mooing masses of Iowans had ever heard of such a thing or such a place!

The arugula controversy raises an obvious question: When did arugula become the undisputed symbol of elitist food — what you might call the anti-cabbage? And what about the other lettuces? Can a politician seeking to connect with ordinary people safely eat anything other than iceberg?

We all know, intuitively, that kale is on the elitist side of the elitist-vulgarian divide, but what about romaine?

"There's nothing wrong with eating arugula," argues May Bogdanovic, owner of Arucola, an Italian restaurant in Washington. She says her restaurant is named after the Italian word for the leafy green, with an extra "A" at the beginning just for flair. "It's one of the healthier leaf lettuces. ... If Obama is worried about the price of arugula, then obviously he has a healthier diet than McCain."

Robert Rossi, co-owner of Field Fresh Farms, a major grower of arugula and other greens in Watsonville, Calif., also defends Obama against the elitist-salad-eater slur.

"I think he has very good taste buds. And I'm a Republican," Rossi says.

But this remains, at core, an Iceberg Nation. According to the United Fresh Produce Association, American farmers grew 6.3 million pounds of "head lettuce" — iceberg — in 2007, more than twice as much as the next-most-popular lettuce, romaine. In fact, the iceberg total is more than romaine, green leaf, red leaf, spinach and every type of specialty lettuce combined.

Iceberg's great virtue is that it is remarkably consistent and doesn't look like something that was ever anywhere near the ground. Arugula, by contrast, is flamboyantly plantlike, and with its vowel-heavy name is clearly foreign, and a reminder, politically, of Obama's exotic biography.

The arugula issue echoes what has become known as the beer-wine divide, also known as the Dunkin' Donuts-Starbucks divide. Republican campaign strategist Mike Murphy wrote in Time magazine that working-class voters are suspicious of Obama, whom they see as one of the overeducated executive-types who are constantly downsizing the workforce: "Deep down, they think he'd rather hit the executive gym for a cardio workout during lunch hour than share a cheesesteak and beer with the hourly workforce."

Some might argue that vegetables and salad dressings should not be assigned political symbolism. But this is an election year. Everything's on the table. And of course you remember that it happened before, with Belgian endive.

That was 1987. Michael Dukakis, like Obama, was in Iowa, and known to be pondering a presidential run. He, too, was talking about how Iowa farmers could diversify their crops. He mentioned, as an example, that they could grow Belgian endive. The Republicans never missed a chance thereafter to whack Dukakis with the endive gaffe.

Along with language and religion, food is one of a culture's defining characteristics. Americans simultaneously embrace exotic foods while being wary of becoming divorced from our red-meat, boiled-potatoes past.

But there's one good piece of breaking news for Obama: McCain in recent days has been making regular forays to a Starbucks. And did McCain get coffee? No: cappuccino.

The arugula of hot beverages.