PITTSBURGH — The rise of the Democratic left in Pittsburgh did not happen overnight. It was built over years through patient organizing, disciplined recruiting, and a clear-eyed focus on the races that mattered most: low-turnout primaries where entrenched power was vulnerable.

Mik Pappas’s 2017 race for Pennsylvania’s 31st Magisterial District judge offered an early hint that the local Democratic establishment was losing its grip on some of the contests it had once taken for granted. He was underfunded, openly aligned with the Democratic Socialists of America (DSA), and not expected to mount a serious challenge. This made his win all the more instructive.