What single-payer advocates want to hear from 2020 Democratic primary contenders

In the fall of 2017, with more than three years to go before the next presidential election, Sen. Bernie Sanders (I-VT) introduced Medicare for All legislation in the Senate. The bill racked up a long list of high-profile co-sponsors, many of whom were already being talked about as 2020 contenders.

Since then, Sens. Elizabeth Warren (D-MA), Kamala Harris (D-CA), and Kirsten Gillibrand (D-NY) — all co-sponsors of Sanders bill — have jumped into the Democratic fray. So, to...