Nugent netted from ten yards less than a minute after coming on as a sub on the hour, before Callum Davidson sealed it four minutes from time.
Davidson capitalised on a mistake by Marcus Bignot to go one-on-one with keeper Simon Royce for the easiest of goals.
The result was Rangers' fourth straight loss and they have won just one in their last six home games.
Visiting keeper Carlo Nash had an impressive first half, keeping out Lee Cook before denying teenager Shabazz Baidoo his second goal in as many games as Rangers' home hoodoo continued.
Baidoo, who was one of the few players to escape manager Ian Holloway's wrath following their loss at Plymouth last weekend, was rewarded with his first start of the season.
Lee Cook made Rangers' first attack of the match after three minutes and it almost paid off as he fired a low shot to the left of Nash.
Baidoo had the ball in the net 15 minutes into the match as he glanced in Kevin Gallen's cross but referee Dermot Gallagher ruled it out for handball.
Preston clearly had the edge over Rangers' slight midfield four and Chris Sedgwick should have scored on 16 minutes but could only spoon the ball over the bar from 15 yards.
Six minutes later it was Gareth Ainsworth who was guilty of blowing a golden opportunity, after Bignot wrestled clear of Callum Davidson.
Bignot crossed to Ainsworth, who was in yards of space but somehow hacked his shot into the away stand.
Baidoo was unlucky half an hour into the first half when he got on the end of a slick move started by Richard Langley.
Langley broke free from Paul McKenna to pass to Cook, who burst up the left to put Baidoo through on goal and it was only a point-blank save from Nash that kept the ball out of the net.
Rangers' chances, watched by a season-low 10,901 people, were few and far between as Preston muscled their way up the midfield.
The visitors looked far more dangerous after Nugent joined the fray and he could have added a second in the 70th minute but he fired wide.
Georges Santos, who came on for Baidoo with 15 minutes to go, should have done better with his effort from 20 yards which rocketed over the crossbar.
Kevin Gallen had a shot cleared off the line with a minute to go and Stefan Moore fired a strong shot straight at Nash in injury time but it was too little too late as the players walked off to a chorus of boos.