Phonological rule innovation is thought to come about via reanalysis of some phonetic variation (e.g., Bermúdez-Otero, 2007; Hyman, 1975; Ohala, 1981; Pierrehumbert, 2001). Yet, empirical evidence suggests instead that the role of phonetic variation during phonological rule innovation is minor (Fruehwald, 2013, 2016). This paper adds to this ongoing debate an empirical analysis of an emergent allophonic contrast—an “/æ/ nasal system”—in White Michigan English. Analyses of speaker-level acoustic data from a sociolinguistic corpus (n = 36) and a subphonemic judgment task (n = 107) suggest that Lansing exhibits gradual phonological rule emergence. Social conditioning appears to act as the catalyst of phonological rule formation and its spread. The mechanism of actuation was thus “the chance alignment of social and phonetic variability” (Baker, Archangeli, & Mielke, 2011), suggesting that social conditioning on phonetic variability must play a major role in phonological emergence.