With a stalemate looking likely, Davidson bundled home a winner 13 minutes from the end to lift Tommy Wright’s side above Hearts into fifth place.
With defences giving little away, both sides struggled to create clear-cut chances in front of fewer than 2000 fans.
But Davidson was on hand to seal a fourth successive Saints win hallmarked by clean sheets after Livi keeper Liam Kelly had fended off a flashing Matty Kennedy header from Richard Foster’s well-worked cross.
Returning Saint Michael O’Halloran made a late cameo after cutting short his stay with Melbourne City while the visitors drafted in Craig Sibbald, Ricki Lamie and their recent recruit from Partick Thistle, Chris Erskine.
With the paperwork completed on a loan deal with Cardiff, defender Ciaron Brown featured among the Lions’ substitutes but pre-match doubts Craig Halkett and Declan Gallagher both turned in solid performances in Gary Holt’s rearguard.
Livingston settled quickly and on-loan Rangers striker Ryan Hardie twice shot from the edge of the box.
His first effort was deflected wide but the next one forced keeper Zander Clark to drop down low to his left to turn it around the post for another corner.
The visitors were almost caught out by a free-kick cutback by Liam Craig into the path of David Wotherspoon in the 28th minute but the midfielder’s net-bound 15-yard thunderbolt was blocked by Alan Lithgow.
Two minutes later Livi skipper Halkett was booked for downing Tony Watt and Craig’s ambitious 35-yard free-kick was tipped over by cautious keeper Kelly.
Ross Callachan sent a low shot skimming wide and Lawless scooped over an Erskine cross as the teams traded attacks before the interval.
Perth full-back Foster picked up a caution on the stroke of half-time for felling Erskine as he surged down the line.
Halkett then teased a tip over from keeper Clark on the hour mark after letting fly with a 30-yard free-kick and the defender headed wide from Erskine’s corner.
A surging Davidson run halted by Scott Pittman prompted referee Andrew Dallas to pull out the yellow card again.
One-time Livi player Davidson picked up a late caution but he had already rounded off an influential display with his second goal of the season.