Early in the 20th century, the Supreme Court established the clear and present danger test as the predominant standard for determining when speech is protected by the First Amendment.

The Court crafted the test — and the bad tendency test, with which it is often conflated or contrasted — in cases involving seditious libels, that is, criticisms of the government, its officials, or its policies. It would be superseded by the imminent lawless action test in the late 1960s.

 

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https://www.mtsu.edu/first-amendment/article/898/clear-and-present-danger-test