The most important battle the American left has waged in generations is presently being fought on the Democratic primary stage. On one side stands Bernie Sanders, the first avowed socialist to come close to the presidency since Eugene V. Debs received 6 percent of the vote in the 1912 election. On the other side stands Elizabeth Warren, a liberal Harvard professor who made her career as an expert in bankruptcy law. The victor in this struggle has the potential to set the course for the next decade, or more, of progressive politics.

Despite their avowed and admitted differences, some pundits have attempted to paper over the distinctions between the two candidates. As New York’s Ed Kilgore aptly summarizes, there is a “prevailing tendency [in the media] to treat Elizabeth Warren and Bernie Sanders as fellow progressives jockeying for position in the left ‘lane’” of the Democratic party.

In fact, it is true that, as Kilgore states, Sanders and Warren in some respects share “very similar policy agendas.” But such similarities obscure the profound differences in their approach and understanding of modern politics. This is nowhere truer than in the realm of foreign policy, the issue area over which American presidents are able to exert the greatest influence.