THE runaway phenomenon that is “Mad Men,” with its stylish depiction of Kennedy-era New York, where men dressed with style and philandered with impunity, has handed modern men their very own “Sex and the City” fantasy.

But an overlooked aspect of “Mad Men” is the fashion turnabout it represents. In the show, the older men  Don Draper and his boss, Roger Sterling  are the best-dressed characters, while the new-kid, cool-cat copywriters are so loath to play the game that they won’t even wear a tie. Soon enough, the hippie movement would deride the necktie as a “dog collar” and any corporate-minded spoilsport as a “suit.” In the decades that followed, a minor genre of films addressed the Unsuiting of Mr. X, from “Barefoot in the Park” (1967) and “Easy Rider” (1969) to “After Hours” (1985) and “Something Wild” (1986).

Now the tie is on the other neck. Today the well-off 55-year-old is likely to be the worst-dressed man in the room, wearing a saggy T-shirt and jeans. The cash-poor 25-year-old is in a natty sport coat and skinny tie bought at Topman for a song. Young men are embracing the “Mad Men” elements of style in a way that the older men never did, still don’t and just won’t. The result is a kind of rift emerging between the generation of men in their 20s and 30s and those in their late 40s and 50s for whom a suit was not merely square but cubed, and caring about how one looked was effeminate.

The evidence of this style gap is everywhere. Just check out the numerous men’s wear blogs  acontinuouslean.com, dandyism.net, thetrad.blogspot.com, fineanddandyshop.blogspot.com  dedicated not to cutting-edge European fashion but to old-school minutiae of dressing well. Or take a look at the Cincinnati Bengals linebacker Dhani Jones, who favors double-breasted suits and bow ties and talks about “the resurgence of the gentleman.”