Lee Lorch follows the financial travails of Stuyvesant Town from his apartment on the brick-lined streets of Toronto’s distillery district.

And though he did not attend a recent meeting of 1,200 tenants, such a session was a familiar occasion for Dr. Lorch, who was instrumental in another tenant-led effort, 60 years ago, to desegregate Stuyvesant Town, the vast apartment complex on the East Side of Manhattan that was recently taken over by its lenders.

He was a leader among the tenants who petitioned and picketed, but ultimately lost a bruising legal battle in 1949, in which the state’s highest court ruled that a private landlord could reject tenants based on race. Dr. Lorch, a mathematician who, at 95, is still writing for scholarly journals, lost a succession of teaching positions for his trouble and ultimately left New York and the country to find work....