According to Gallup, some 47 percent of American adults identify as Democrats or lean Democratic, which translates to roughly 10 million more supporters than the Republican Party has. Political scientists rate the national mood as the most liberal it has been since the early 1960s.

Yet despite the premise of majoritarian democracy that favorable public sentiment should translate into political advantage, progressive Democrats do not get what they want in national policy — nothing even close to it. In fact, often they often get the opposite of what they want, then get wiped out in elections anyway. On matters like gun control, health care, taxation, immigration, aid for the impoverished and many other issues, Democrats have lost, and lost again, even when they managed to gain control of both houses of Congress and the presidency.

There are many well-known reasons for this, including the outlandish legislative power of corporate interests and a Constitution that favors rural areas over cities. But does some of it stem from the fact that Democrats have been too willing to compromise or bargain in good faith? Yes, at least new empirical research suggests: Liberals tend to be suckers.

Understanding this suckerdom, and the emerging urge from progressives to avoid it, may be one key to understanding the 2020 primaries, and the rise of uncompromising figures like Bernie Sanders. Sanders may be, as his critics say, incapable of working with others. But for progressive Democrats sick of losing for decades on end, that’s actually his selling point.