Tonight, Chicago PD, a Chicago Fire spin-off, premieres on NBC. Chicago Fire has been a solid success story, growing into the usual broadcast winner of the Tuesday 10PM timeslot (though it regularly was beaten by FX’s Sons of Anarchy.) However it is not the sort of runaway hit that usually inspires spin-offs. Wednesday has been a weak spot in NBC’s line-up, with Ironside tanking in the 10PM timeslot earlier this season. Last night, without the benefit of The Voice as a lead-in, Chicago Fire garnered a 1.9 adults 18-49 rating. Ironside’s premiere earned a 1.3 adults 18-49 rating. How do you think Chicago PD will fare tonight?