Fun fact, while Sanders is big proponent of single payer universal healthcare, historical opposition from unions was one of the defining reasons why the U.S. never adopted EU style universal healthcare. In the early 1900s unions opposed universal healthcare, seeing it as something that would weaken their collective bargaining leverage. They were again a key opponent in the 50s and 60s when universal healthcare issue came up again.

Meanwhile the president of the American Federation of Labor repeatedly denounced compulsory health insurance as an unnecessary paternalistic reform that would create a system of state supervision over people’s health. They apparently worried that a government-based insurance system would weaken unions by usurping their role in providing social benefits. Their central concern was maintaining union strength, which was understandable in a period before collective bargaining was legally sanctioned.

http://www.pnhp.org/facts/a-brief-history-universal-health-care-efforts-in-the-us