Those many Republicans banking on public inattention to the sordid tales of GOP corruption may not want to pick up today’s Post anytime soon — Sex has entered the equation. “Federal authorities are investigating allegations that a California defense contractor arranged for a Washington area limousine company to provide prostitutes to convicted former congressman Randy ‘Duke’ Cunningham (R-Calif.) and possibly other lawmakers, sources familiar with the probe said yesterday.” Uh, oh…DC just loves a good sex scandal, right, guys? Update: The limousine firm in question denies the allegations.