He was one of the Hollywood Ten, a group of screenwriters and directors who were cited for contempt of Congress and blacklisted for their refusal to testify regarding their alleged involvement with the Communist Party.

His father was a Marxist garment industry union organiser, and Lester developed his socialist ideology at a young age.

In 1933, he teamed with John Howard Lawson and Samuel Ornitz to establish the Screen Writers Guild, and in 1934 he joined the Communist Party (CPUSA).

[6] In 1947, he became one of the Hollywood Ten who refused to answer questions before the House Committee on Un-American Activities (HUAC) about their Communist Party membership.

[7] He replied that it wasn't a simple "Yes|No" matter but required a more complete response that he had prepared in a written statement.

[7] Cole was convicted of contempt of Congress, fined $1,000 and sentenced to twelve months' confinement (along with fellow Hollywood Ten member Ring Lardner Jr.) at the Federal Correctional Institution at Danbury, Connecticut, of which Cole served ten months.

In it, he recounted a 1978 incident when he phoned into a radio talk show on which ex-Communist Budd Schulberg was a guest.

"[17] The fact that Cole chose to cite it in his autobiography shows how even decades after the HUAC hearings, bitterness still existed between friendly and "unfriendly" witnesses.