Berwick's promotion prospects plunged as runaway leaders Partick took another step towards the championship with a 1-0 win.
Rangers failed to pick up the outstanding Danny Lennon after 55 minutes when he broke clear on the right to cross for Michael Hardie who hammered in his 15th goal of the season.
Six minutes later, Alan Neill missed a chance to equalise, shooting high over from the penalty spot after Marc Anthony had been pushed off the ball in the area.
The final blow came when Anthony was sent off after being shown a second yellow card after protesting when referee Calum Murray had already given his side a free-kick.
Both sides worked hard and passed the ball well, but well-balanced Thistle were always the likely victors.