Part 1 of this series¹ ended with the start of the Great Migration of African Americans, many of them Republicans, from the South to cities in other parts of the country. Abroad, several nations were waging World War I.

Suffering heavy losses and other hardships in World War I, the Russian military was verging on mutiny. In 1905, Russian civilians had attempted a revolution, resulting in significant reforms, including the Russian Constitution of 1906, but not in conclusive victory for the revolutionaries. In March, 1917 (February, Julian calendar), they attempted a second revolution. Leaders of the Russian military did not try to suppress it, but, again, the revolutionaries did not prevail.² Russia went on with a loose(ish) form of dual government. In 1917, the U.S. entered World War I.

In November, 1917 (October, Julian calendar, hence, the "October Revolution"), Russians revolted and prevailed, resulting in the Russian Soviet Federative Socialist Republic (and the Russian Civil War). In 1918, the deposed Tsar, Nicholas Romanov, and his family, including children, were shot summarily. (While drafting this post, I learned the shooting is currently being investigated. https://en.wikipedia.org/wiki/Execution_of_the_Romanov_family)

The events in Russia had to have sent shock waves through the world's rich and powerful, both in and out of government. By early in 1919, a rapidly-growing Communist Party had already been established in the United States, no doubt causing apprehension among the ruling and upper classes and among employers at almost every social stratum. As had the socialists, anarchists and other leftists in last half of the Nineteenth Century, the American Communist Party played a prominent role in the U.S. labor movement from the 1920s through the 1940s,³ including a major role in founding most of the country's first industrial unions (which, ironically, later used the McCarran Internal Security Act to expel Communist members). It also opposed racism and fought for integration.

Historian Ellen Schrecker concludes that decades of recent scholarship[6] offer "a more nuanced portrayal of the party as both a Stalinist sect tied to a vicious regime and the most dynamic organization within the American Left during the 1930s and '40s".[7]

By August 1919, only months after its founding, the Communist Party claimed 50,000 to 60,000 members. Members also included anarchists and other radical leftists. At the time, the older and more moderate Socialist Party of America, suffering from criminal prosecutions for its antiwar stance during World War I, had declined to 40,000 members. The sections of the Communist Party's International Workers Order organized for communism around linguistic and ethnic lines, providing mutual aid and tailored cultural activities to an IWO membership that peaked at 200,000 at its height.

https://en.wikipedia.org/wiki/Communist_Party_USA

In my perception, this wiki description fails to underscore that, for obvious reasons, many ordinary blue collar workers, especially "labor union Democrats" (Hillary's "hard-working white people?"), joined this U.S. branch of the Workers' Paradise, and only not wild-eyed radicals. Its appeal to African Americans and their supporters in the 1920s is also obvious. As Americans were later to learn in insane detail, the American Communist Party also appealed to those in the entertainment industry, which had begun to organize circa 1880. https://www.amazon.com/Actors-Organize-History-Formation-1880-1919/dp/07... (Coincidentally(?), Actors Equity struck in 1919.) Many members of the industry were also early supporters of equal rights. Therefore, the appeal to members of the Communist Party to the entertainment industry is obvious, too. (Stalinist "sect tied to a vicious regime?" Who edited this wiki? J. Edgar or Jackass Joe?)

Mary Pickford in 1919 film, Daddy Long Legs

¹ http://caucus99percent.com/content/presidential-elections-and-liberals-l... Much of Part 1 and this post relied heavily on various wikipedia articles, though I used some other sources as well.

² Keeping the troops already angered by World War I away from the revolutionaries may have been a brilliant move by military leaders to protect the government. In the third and successful attempt at revolution, the military did join the revolutionaries, which had not been the case with the prior two unsuccessful attempts. Pure speculation: This may be why the U.S. military has tended to be more right wing than the U.S. population as a whole. Given the examples of the French Revolution and the October Revolution, when good numbers of the military either deserted and/or joined the revolutionaries, the PTB may well prefer a military that does not lean left.

³ While I try not to get ahead of myself chronologically: It's "from the 1920s" because the party was founded in 1919; and it's "through the 1940s" because of World War II and the concomitant xenophobia and defensive paranoia, followed by the McCarthy hearings. And the rest, as they say, is history.