Crawley came from behind to win for the first time on Boxing Day for 11 years at Fratton Park.
An own goal from Claude Davis put Portsmouth ahead after just ten minutes but Reds were level at half-time through Mat Sadler's maiden goal for the club.
Billy Clarke scored his ninth of the season with 17 minutes to go to secure back-to-back away wins for Reds and lift them to eighth in League One.
Pompey caretaker boss Guy Whittingham made the big decision to drop top scorer Izale McLeod in favour of Benson.
That call was repaid when the striker was credited with the opening goal after ten minutes, although there was a strong suspicion it was Davis who got the decisive touch as he tried to defend Scott Allan’s low ball in from the left.
Crawley probably felt a little hard done by to find themselves behind after making a positive start with Nicky Adams twice getting behind the Pompey defence.
Reds continued to press and should have equalised after 26 minutes when a cross from Adams looped up off the leg of a defender to Hope Akpan ten yards out only to put his header straight at Simon Eastwood.
Two minutes later Crawley were level as Sadler scored for only the second time of his career. There was a touch of fortune about it as he swung over an inswinging free kick from the right which cleared everyone and caught out Eastwood on its way into the far corner.
The visitors were looking the most threatening and had to fine opportunities to take the lead before the interval.
Akpan blazed a shot over from ten yards with the goal at his mercy and Gary Alexander was just unable to get a touch to a cross from Adams at the far post.
Portsmouth were also looking dangerous with Mustapha Dumbuya shooting over the bar after a penetrating run and Nathaniel Mendez-Laing putting the ball into the back of the net only for the goal to be chalked off for offside.
The game became even more open in the second half with neither side happy to settle for a point.
Adams had an effort deflected just wide off the legs of Gabor Gyepes while balls flashed across the face of goal in both boxes.
It was Reds who get their noses in front with 17 minutes to go when a cross from Adams was flicked on and Clarke got ahead of his man to toe it home from close range.
Rather than sit back, Crawley went looking for a third with Adams forcing Eastwood into a sharp save and Alexander’s follow-up effort blocked by a defender.
Pompey cranked up the pressure in the final ten minutes but Reds were able to hold on to secure their sixth away win of the season.