The world we live in today was made possible by the neoliberalization of historically left parties. Why that happened is what sociologist Stephanie L. Mudge examines in her monumental book Leftism Reinvented: Western Parties From Socialism to Neoliberalism. Leftism Reinvented traces the long history of the UK’s Labour Party, the Swedish Social Democratic Party, the Social Democratic Party of Germany, and even our very own Democratic Party.

To understand why these parties became neoliberalized, however, she first examines how they were founded — in all cases but the Democratic Party — as thoroughly socialist parties, and how they made the switch from socialism to Keynesianism in the mid-twentieth century. What she found out might surprise you.

The changing position and role of party economic experts, she argues, was critical. And it proved critical again with the shift from Keynesianism to neoliberalism. Mudge writes that the power of these experts was destabilized by economic crises, which put reigning orthodoxies into sudden question. First, the gold standard–bound economic crises of the early twentieth century, which culminated in the Great Depression and the rise of fascism. And then, second, the oil shock–fueled stagflation crisis that dominated the 1970s. Each of these crises opened an interpretive battle that saw incumbent experts and their ideologies dethroned. First, the Marxists were displaced by the Keynesians. And then the Keynesians were displaced by a neoliberalized combination of finance experts, wonks, and strategist spin doctors.