In 1929, Lambert joined the Communist Party in California. She served as state organizational secretary until the mid-1940s. In this critical role, Lambert was "second in command of the state CP." Lambert was active in major strikes of the early 1930s, including the 1933 San Joaquin Valley Cotton Strike and the 1934 San Francisco General Strike. During the General Strike, she was arrested, along with Communist activist Ida Rothstein, on charges of vagrancy; both women were acquitted. Lambert also participated in local politics, running for the San Francisco Board of Supervisors in 1931 and 1933 as the official Communist Party candidate, and winning 10,815 votes in the 1933 election. In both elections, Lambert was the only woman candidate.