Communist League of America (Opposition)

The Communist League of America (Opposition) was founded by James P. Cannon, Max Shachtman and Martin Abern late in 1928 after their expulsion from the Communist Party USA for Trotskyism. The CLA(O) was the United States section of Leon Trotsky's International Left Opposition and initially positioned itself as not a rival party to the CPUSA but as a faction of it and the Comintern. The group was terminated in 1934 when it merged with the American Workers Party headed by A. J. Muste to establish the Workers Party of the United States.

On October 27, 1928, three leading members of the Workers (Communist) Party of America were expelled from the organization for the transgression of "Trotskyism." The trio — Communist Labor Party founder James P. Cannon, Labor Defender editor Max Shachtman, and Romanian-born former head of the Young Workers League Martin Abern — had been won over to the ideas of Leon Trotsky when Cannon had been exposed to a translation of Trotsky's manuscript "The Draft Program of the Communist International: A Criticism of Fundamentals" while a delegate to the Sixth World Congress of the Comintern in Moscow that summer.

Cannon later recalled:

"Through some slip-up in the apparatus in Moscow, which was supposed to be bureaucratically airtight, this document of Trotsky came into the translating room of the Comintern. It fell into the hopper, where they had a dozen or more translators and stenographers with nothing else to do. They picked up Trotsky's document, translated it and distributed it to the heads of the delegations and the members of the program commission. So, lo and behold, it was laid in my lap, translated into English! Maurice Spector, a delegate from the Canadian Party, and in somewhat the same frame of mind as myself, was also on the program commission and he got a copy. We let the caucus meetings and the Congress sessions go to the devil while we read and studied this document. Then I knew what I had to do and so did he. Our doubts had been resolved... We made a compact there and then — Spector and I — that we would come back home and begin a struggle under the banner of Trotskyism."

...
Wikipedia