It’s one of the most vexing challenges facing the labor movement: how to wield influence in an era increasingly dominated by technology giants that are often resistant to unions.

Are workers best served when unions take an adversarial stance toward such companies? Or should labor groups seek cooperation with employers, even if the resulting deals do little to advance labor’s broader goals?

The debate has flared up around labor’s efforts to make inroads with the likes of Uber and Airbnb, businesses that allow drivers and homeowners to earn income as contractors. And it was on vivid display in the political battle over Amazon’s plan to create a new headquarters in New York with 25,000 jobs.

The plan fell apart in the face of a backlash over public subsidies, resentment of the covert process in which the city and the state negotiated the deal, and concern about its neighborhood impact. But labor issues were also a factor, giving rise to tensions even among unions.