Bennett and Naismith on target at Fratton Park.
Pompey got their promotion charge back on track as they returned to winning ways against struggling Newport.
Kyle Bennett opened the scoring late in the first half before Kal Naismith headed in a second after the interval.
It appeared that the Blues were cruising towards three points, but Alex Samuel netted for the visitors to ensure a nervy finale.
Paul Cook – in his 100th match in charge – made two changes from the side beaten at Stevenage the previous week.
Bennett and Naismith had both recovered from injury to take their place in the starting 11, with Noel Hunt dropping to the bench and Christian Burgess serving a one-match ban.
There was a minute’s silence before kick-off in tribute to those affected by the recent attack in London.
Pompey soon started to dominate once the action got underway, but struggled to create too many clear-cut chances.
The best ones fell to Eoin Doyle, but twice he just failed to get on the end of teasing deliveries from Naismith.
And the on-loan Irishman was then unable to beat County keeper Joe Day from an acute angle after being slipped through by Carl Baker.
But the striker was forced off midway through the first half after picking up an injury and replaced by Conor Chaplin.
There had not been much for David Forde to worry about and when former Blues striker Ryan Bird cut the ball across the face of goal, Tom Davies and Michael Doyle combined to scramble it clear.
But it was still Pompey causing the most problems, even if Day was not exactly being over-worked between the sticks.
Bennett and Matt Clarke both had shots charged down, while a number of corners were comfortably dealt with.
The Blues did break the deadlock just before the break, however, and it was a goal that was extremely easy on the eye.
Baker intercepted the ball from Bird and slipped a superb pass through the Newport defence for BENNETT, who neatly slotted home.
Newport County 0
After seeing off some Newport pressure early in the second half, the hosts went in search of another goal.
Chaplin was never really going to trouble Day with an audacious attempt from wide on the left, while Baker’s effort rose over the crossbar.
Naismith then hit a cleanly-struck free-kick straight into the keeper’s arms, as the Blues started to take control.
They almost doubled their advantage on 58 minutes, but Chaplin – who wanted the pass played earlier – could not quite convert Gareth Evans’ low cross.
But Pompey did strengthen their lead just seconds later, as Bennett found Chaplin, who neatly chipped the ball up for an unmarked NAISMITH to head into the net.
Their attacking intent did not end there, though, and Naismith saw a corner deflected into the side netting, while his second attempt was just too high for Clarke at the far post.
It was not quite one-way traffic and Naismith eventually hacked the ball clear after a County corner caused some problems.
Bennett received hearty applause from the Fratton faithful when he made way for Jamal Lowe on 71 minutes.
But it was the visiting support almost cheering when Marlon Jackson sent the ball curling towards goal, only for Forde to make a fine save.
Newport did reduce their deficit moments later, though, with Samuel rising to convert Sean Rigg’s cross from the right.
And they come close to equalising on 78 minutes as the hosts started to get sloppy, with Forde coming off his line to deny Jackson.
County’s confidence had risen and Jack Whatmough replaced Naismith as Pompey tried to shore things up.
The nerves were starting to grow inside Fratton Park and Evans did well to take the ball off the foot of Samuel as he shaped to shoot.
But the Blues saw out the closing stages with relative ease to seal a valuable victory in the battle for promotion.
Pompey (4-2-3-1): Forde; Evans, T.Davies, Clarke, Stevens; Rose, M.Doyle (c); Baker, Bennett (Lowe 71), Naismith (Whatmough 83); E.Doyle (Chaplin 25)
Goals: Bennett 42, Naismith 59
Subs not used: O’Brien, Talbot, Linganzi, Hunt
Newport (4-2-3-1): Day; Pipe, Jones (Randall 71), Demetriou, Butler; Labadie (c), Bennett; Samuel, Rigg, Owen-Evans (Myrie-Williams 46); Bird (Jackson 46)
Goals: Samuel 75
Booked: Rigg, Labadie, Myrie-Williams
Subs not used: Bittner, Barnum-Bobb, Nelson, Gordon
Referee: Tim Robinson
Attendance: 17,364 (322 away fans)