It was a fourth successive victory for Partick, who also extended their unbeaten run to nine matches.
Pre-game leaders Falkirk suffered a second successive defeat as they went down 1-0 at Peterhead.
Cove Rangers saw their eight-game unbeaten run ended by a 1-0 defeat at Montrose.
Fraser Fyvie's own goal put Montrose ahead in the 15th minute, with Rangers' night ending in further misery when Ryan Strachan was dismissed in the closing stages.
Clyde moved out of the relegation play-off place thanks to a 3-1 win at bottom-of-the-table Forfar.
Scott Fenwick fired Forfar ahead seven minutes before half-time but Lewis Jamieson levelled immediately and added a second just past the hour mark.
Joshua Jack secured a vital victory with eight minutes left as Clyde snapped a four-game losing streak and leapfrogged a point above Dumbarton.
Callum Gallagher opened the scoring in the 66th minute and Dale Carrick added a second, converting at the second attempt after seeing his penalty saved, 11 minutes later.