The tagline for Showtime’s The Borgias, about the very powerful, very corrupt clan that dominated Renaissance-era Rome, is “The Original Crime Family” — just the sort of super-competitive, bald-faced attempt to steal some of HBO’s mob thunder (what, you have Tony and Atlantic City and ancient Rome? We have their ancestors. Well, not the very last one’s ancestors … ) that we like to see from a network that could just as easily have positioned The Borgias as a follow-up to their own The Tudors (which it also is). The tagline is basically a promise, not of quality, but of decadence: There will be as much violence, nudity, scandal, extravagant sets, and backroom scheming as can be crammed into a period show that takes place before the regular deployment of gun violence. Even better, there will be blasphemy. Jeremy Irons plays the pater familias, Rodrigo Borgia, a powerful, ruthless, ethically moribund priest with multiple children and mistresses who became Pope Alexander VI in 1492, when the show takes place. Two of his children in particular, Cesare and Lucrezia, went on to become cutthroat legends in their own right. (And though dogged by incest rumors, in the trailer we think Cesare’s not making out with his sister, but a love interest who just has the exact same shade of blonde hair.) It’s these three Borgias — led by Irons, who does chilly, sensual over-the-topness better than just about anyone — who will dominate the sordid goings-on. Whether the result will make for good television (it’s being executive produced by Neil Jordan), or lusty, fetid, campy good television, we’ll have to wait and see.