United, on the other hand, remain hot on the heels of Hearts in the race to be the third force in Scottish football.
The visitors should have opened the scoring with only 50 seconds on the clock as Francisco Sandaza flicked the ball to an unmarked Jon Daly practically on the goal-line, but Mark Howard pulled off a stunning point blank save to foil the Terrors.
The Buddies began to force their way into the match with their first real chance falling to American import Andy Dorman, but the midfielder ballooned his half-volley over the bar after being set up by Dennis Wyness.
Michael Kovacevic garnered favour with his manager just after the half-hour mark as the hulking full-back prevented what seemed like a certain Saints goal as Dorman ran clean through on goal, but the defender was able to stretch out a leg just as the Buddy was about to pull the trigger.
The Tangerines immediately marched up the pitch and managed to forge the breakthrough in the tussle.
Willo Flood managed to bustle his way to the byline and deliver a back-post cross for Daly to rise and power his header into the back of the net.
It looked like it would be a long afternoon for the Paisley side in the 51st minute as Wyness was presented with one of the easiest chances of his career courtesy of Craig Dargo.
The former Aberdeen striker was unmarked six yards from goal but inexplicably sliced his shot over much to the fury of the home support.
Dorman was looking the sharpest of McPherson's men and again burst into the box looking likely to score. Gary Kenneth was the hero in this instance with a well-timed tackle.
Daly almost doubled his tally in the 75th minute as the striker connected well with a volley from just outside the box forcing Howard into another fine save.
Stephen McGinn was desperately unlucky not to claw the Buddies back into the match in the 82nd minute as the winger drilled his effort off the bar.
St Mirren retained possession but seconds later were foiled again as an unmarked Billy Mehmet blasted over the bar from six yards out.
The home side's misery was compounded in the 88th minute as Jack Ross felled Craig Conway in the box.
Daly gleefully stepped up to drive the spot-kick low into the corner for his second of the match.