Spector was born in the Russian Empire and immigrated to Canada with his family as an infant. He graduated from Queen's University and practiced labour law in Toronto when he wasn't employed in political positions.
First radical political activity
Spector was influenced by Trotsky's work The Bolsheviki and World Peace, which was published in the Toronto Mail and Empire in January 1918, and by Social Democratic Party of Canada Dominion Secretary Isaac Bainbridge who introduced him to Lenin's writings and inspired him to join the SDP. Spector engaged with the left-wing of the Canadian SDP, and eventually left to form the Communist Party of Canada.
Turn to Trotskyism
In 1928, Maurice Spector, while attending the Sixth Congress of the Comintern in Moscow, accidentally got hold of a copy of Trotsky's Critique of the Draft Programme of the Communist International, which criticised the position of Nikolai Bukharin and Joseph Stalin, and especially exposed the anti-Marxist theory of "socialism in one country". This critique was a landmark in the ideological arming of the International Left Opposition. In a truly prophetic statement, Trotsky warned that if this position were adopted by the Communist International, it would inevitably mark the beginning of a process that would lead to the nationalist and reformist degeneration of every Communist Party in the world. Three generations later, his prediction - which was ridiculed by the Stalinists at the time - has been shown to be correct. Stalin had no intention of circulating Trotsky's document. But by a strange accident of history, that is what happened. At that time, when the Stalinist regime had not yet been consolidated, the Communist International still had to observe certain norms of democratic centralism, which permitted the circulation of minority opinions. Although Trotsky had been expelled from the Russian party a year earlier, he took advantage of the Congress to appeal to the Communist International. In the process he submitted his document on the Draft Programme. Through a blunder in the apparatus, they circulated Trotsky's document to the heads of the delegations, including members of the programme commission. It was here that the AmericanJames Cannon and Maurice Spector first saw and read Trotsky's document. Cannon recalled:
"Through some slip-up in the apparatus in Moscow," recalls Cannon, "which was supposed to be 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 programme commission. So, lo and behold, it was laid in my lap, translated into English by Maurice Spector, a delegate from the Canadian party, and in somewhat the same frame of mind as myself, was also on the programme 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. It was as clear as daylight that Marxist truth was on the side of Trotsky. We had a compact there and then - Spector and I - that we would come back home and begin a struggle under the banner of Trotskyism."
In 1932 he co-founded, with Jack MacDonald, the Workers Party of Canada. This new organization represented the first Canadian section of the International Left Opposition.
Leaving Canada
Spector moved to New York City in 1936 and became a leading member of the Trotskyist movement there. He presented the International Report at the founding convention of the Socialist Workers Party at the end of 1938, but dropped out of the party in 1939.. He joined the Socialist Party of America shortly after leaving the SWP in 1939, and remained on its executive body until 1958, when he resigned after breaking with Max Shachtman and his proposal to merge Shachtman's Independent Socialist League with the Socialist Party and Spector anticipated this would move the SP rightwards. In his later, Spector became editor of a children's magazine published by the Labour Zionist movement.
Deportation threat
Canada had revoked Spector's citizenship and, in 1941, the Federal Bureau of Investigation learned that Spector was in the United States illegally and had him detained. As Canada refused to accept him, the United States began proceedings to deport him to the Soviet Union. The American Civil Liberties Union defended Spector on the grounds that, as a Trotskyist, his life would be in danger were he deported to the USSR. Spector eventually regained his Canadian citizenship and was permitted to remain in New York.