What distinguishes Sanders is the same quality that distinguished him on domestic policy in 2016: his willingness to cross red lines that have long defined the boundaries of acceptable opinion. One clear example is Israel. Most of the Senate Democrats running for president have shifted left on the subject. Booker, after initially supporting legislation to criminalize boycotts of the Jewish state, voted against a similar bill last month. Warren, after defending Israeli military actions in the Gaza Strip earlier in her career, last year criticized Israel’s response to protests there. But Sanders has gone much further: He’s produced videos that call Gaza an “open-air prison,” he’s depicted Benjamin Netanyahu as part of the “growing worldwide movement toward authoritarianism,” and, most controversially of all, he’s suggested cutting U.S. military aid to Israel.

But Israel is only the beginning of Sanders’s sacrilege. He’s the only presidential candidate in recent memory who regularly describes the Cold War not as a heroic American victory, but as a cautionary tale. Sanders doesn’t just warn against U.S. military intervention in Venezuela, as Warren and Gillibrand have. He warns against it while invoking the United States’ “long history of inappropriately intervening in Latin American countries.” In his speech at Westminster College in 2017, he spent paragraph after paragraph detailing America’s disastrous 20th-century interventions: Iran, Chile, El Salvador, Guatemala, Vietnam—a litany that resembled a Noam Chomsky lecture more than a typical presidential candidate’s foreign-policy speech.