To what 1937 fdr plan does the cartoon probably refer? did fdr follow through with that plan? why or why not

The cartoon probably refers to the Court packing plan.

In 1937, President Franklin D. Roosevelt proposed a Judicial Procedures Reform Bill, which intended to expand the Supreme Court. This plan pretended to add one new judge to the federal judicial system for every active judge over the age of seventy up to a maximum of fifteen judges.

This proposal was understood as an act to pack the Court with justices who would support Roosevelt's New Deal, since the US Supreme Court hadn’t approved several New Deal economic measures during the Great Depression.  The plan was known as the "Court-packing Plan". Although the 1937 FDR plan failed in Congress, by the end of 1941 Roosevelt managed to achieve his proposal by serving twelve years in office which allowed him to appoint eight justices to the Court.

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