They are going to choose who they want to piss off.
They fear that advocating a government-run health care system could alienate suburban and upper-income voters who are otherwise eager to eject Mr. Trump from office, while the most progressive immigration policies might turn off the working-class white voters who backed Mr. Trump after twice supporting former President Barack Obama.
Yet for many Democrats, especially those who are younger and not white, the risk in 2020 is not about being seen as overly liberal. Rather, it is nominating a Democrat who is perceived as insufficiently ambitious by voters who were uninspired by Hillary Clinton in 2016 and supported third-party candidates or sat out the election.
There's no candidate they can choose that isn't going to put off some group of people.