Ray McKinnon’s side remain in fourth position after this latest setback, ten points behind leaders Hibernian.
Saints’ recent revival had shuddered to a halt with the Scottish Cup defeat at Celtic Park, the first of three games without a win for Jack Ross’s side. But they bounced back against United to close the gap on second-bottom Ayr United to a point.
The Tannadice side have hardly had their own problems to seek since the turn of the year, of course, so both sides had reasons to be fearful going into this contest.
The home team appeared full of confidence, however, and went for the jugular from the start, opening the scoring while some spectators were still finding their seats.
Willian Edjenguele had no need to foul Rory Loy in the first place but, with everyone back, United should have been able to make a better fist of defending the free-kick.
As it was, their defence was guilty of ball-watching as Stevie Mallan’s cross was headed on first by Loy and then by John Sutton before Harry Davis, the centre-half on loan from Crewe Alexandra, scrambled it behind United goalkeeper Cammy Bell from close range.
United gradually came more into it but it was still against the run of play when Tony Andreu steered Simon Murray’s driven cross behind Billy O’Brien for the equaliser.
The home side refused to be rattled, though, and a goalkeeping gaffe saw them go in at the break a goal to the good.
Willo Flood’s foul on Loy on the far touchline did not seem like a promising goalscoring position but Bell totally misjudged the flight of Mallan’s free-kick from 35 yards and could not get across in time to keep the ball out at his near post.
Andreu came close to equalising for a second time in the 48th minute when his header from Murray’s cross rebounded from O’Brien’s left-hand post.
However, it was the hosts who drew blood next, Lewis Morgan scoring at the third time of asking after strikers Loy and Sutton had failed to put away Cammy Smith’s inviting cross.
Andreu was United’s best hope of salvaging a point and he reduced the leeway with a superb solo goal, dropping his shoulder to elude marker Jack Baird and then beating O’Brien with a venomous drive from 18 yards.
It wasn’t enough and Saints held on for three precious points in their quest to beat relegation to the third tier of the Scottish game for the first time in their history.