I saw this cocktail listed in Imbibe magazine. It's basically a negroni without the Gin. Anyway, I've found it to be pretty tasty. I've been drinking rye versions with either WT or Rittenhouse BIB. I also use less Campari and sweet vermouth -- 3/4 oz each.
The Boulevardier
1 1/2 oz. bourbon
1 oz. Campari
1 oz. sweet vermouth
Stir long and well in a mixing glass with ice.
Strain into cocktail glass.
Garnish with orange, lemon twist, or cherry.