Portsmouth keeper Jamie Ashdown wiped worried frowns from the faces of the QPR faithful when he allowed a long-range Adel Taarabt shot to squirm off his right palm and dribble over the line just before the hour.
Until then, the home fans had witnessed a sterile performance from the Championship leaders, who had barely created a chance up until that point.
Lucky boy: Taarabt shoots to score the opener, but it should have been saved
After it, Rangers were released from their own torpor, and they guaranteed victory 17 minutes from time when an impeccably delivered Taarabt corner was met by Clint Hill powering home a close-range header.
Their five-point lead at the top was preserved. A lacklustre display had still managed to yield three precious points, while sending visitorsPortsmouth to within two places of the relegation zone.
That seals it: Clint Hill (right) celebrates scoring QPR's second goal
After his sulk in the goalless draw at Hull on Saturday, during whichhe turned his back on play and asked to be substituted just before half-time, Taarabt was purged of his negativity by the adoration of his home supporters.
Relieved QPR manager Neil Warnock said: 'Adel let himself down a little bit on Saturday but he's only 21, there's a lot of things going on his mind and he was sensible tonight.
'With the scouts coming to watch him on Saturday, I was absolutely delighted by the timing of his strop. I said on the bus coming home, "There's no chance of them coming in for him now".'
It was Portsmouth, with their minimal squad and after tumbling down the table in recent weeks, who were the more dangerous in the first half.
Dave Kitson looped the ball over Paddy Kenny from a tight angle, onlyfor the ball to land on the roof of the net.
The QPR keeper then flew to his left to turn a pile-driver of a free-kick by Greg Halford away for a corner, which Halford then headed narrowly over.
Stung by Warnock's halftime words and aided by Ashdown's calamity, Rangers were still indebted to a point-blank reaction save from Kenny topush over a Nadir Ciftci header two minutes from time.
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Explore more:People: Neil Warnock, Greg Halford, Dave Kitson, Jamie Ashdown