The action that is often viewed as the most serious attempt to undermine the independence of the judiciary is: President Franklin D. Roosevelt's plan to reorganize the Supreme Court.
Starting from 1933 to 1939, President Roosevelt instituted some social reforms that were meant for the betterment of America. The Supreme court opposed many of those deals and the President was not happy about this.
He set out to reorganize the Supreme Court and this was considered as the most serious attempt to undermine the independence of the judiciary.
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