They originally settled on Hester Street in Manhattan's Lower East Side, but later moved to 2155 Daly Avenue in the Bronx.

While imbibing all the ideological currents in the vibrant New York Yiddish and English radical press, he was particularly attracted to the ideas of Daniel De Leon.

(During the early 20th century such name changes were a common practice for Jewish immigrants who encountered widespread antisemitism in American society.)

That year he also began studying at NYU Law School, but dropped out to pursue a career as a full-time Communist party member.

He stayed with this group after it reversed its stance, and joined the National Organizing Committee in founding the Communist Party of America on September 1, 1919, at a convention in Chicago.

Lovestone was a close adherent of the Pepper–Ruthenberg tendency, which was to be centered in New York City and to favor united-front political action in a "class Labor Party", as opposed to the Foster–Cannon group, which tended to be centered in Chicago and were most concerned with building a radicalized American Federation of Labor through a boring from within policy.

[citation needed] In 1925 the leader of the Pepper–Ruthenberg faction, John Pepper, returned to Moscow for work in the apparatus of the Communist International, raising Lovestone's status to that of a chief lieutenant in a new Ruthenberg–Lovestone pairing.

Foster and Cannon, on the other hand, parted ways, with Alexander Bittelman assuming the mantle as Foster's chief factional ally, while Jim Cannon built his power base in the party's legal defense mass organization, the International Labor Defense (ILD).

[6] When he returned to the US, Lovestone was forced to pay for his insubordination and was expelled from the party for his support of Bukharin and the Right Opposition and for his theory of American exceptionalism, which held that capitalism was more secure in the United States and thus socialists should pursue different, more moderate strategies there than elsewhere in the world.

In 1944, David Dubinsky arranged to place Lovestone in the AFL's Free Trade Union Committee, where he worked out of the ILGWU's headquarters.

[7] In 1973, AFL–CIO president George Meany discovered that Lovestone was still in contact with Angleton of the CIA, who was conducting illegal domestic spying activities, despite being told seven years earlier to terminate this relationship.

[9] Lovestone's successor, Ernie Lee, maintained a low profile during his tenure from 1974 through 1982 and significantly scaled back the AFL–CIO's aggressive advocacy of a hawkish, anti-détente foreign policy.