Marcantonio antagonized conservatives right away. In those days historic loyalties mattered more than ideology in determining party membership, so the divides within parties were far greater. Socialists such as Marcantonio might work together with Republicans and Democrats from neighboring districts in New York while fighting the political efforts of both parties’ members from other regions.

But even progressive Democrats of Franklin Roosevelt’s party came under attack from Marcantonio. In 1935 he criticized the Social Security Act as inadequate, calling instead for a social-welfare benefit that would be government-funded but administered by labor unions. In Ocasio-Cortez and her “Squad” we can see echoes of this intransigence. While many Democrats today have goals that Marcantonio would appreciate, they tend to take a more prudent approach, gradually ratcheting up state control so most people scarcely notice it.

Ocasio-Cortez, like Marcantonio, has no time for half-measures and is, at least, honest about her plans to remake society. Yet in calling for more immediate radical changes, she and the Squad end up alienating their colleagues and shifting all the legislative power to the incrementalists. LaGuardia understood this: He remained progressive, but not to the extent that his voters were repelled by his views. Here is where, if she were so inclined, Ocasio-Cortez could learn from the past and refine her tactic. (She won’t.)