Ronald Radosh, born on January 1, 1937, in New York City, is an American historian, author, professor, former New Left activist, and political commentator known for his ideological journey from Marxism to conservatism, becoming a prominent conservative critic of communism and leftist movements. Raised in a family of Ashkenazi Jewish immigrants who were active members of the Communist Party USA (CPUSA), Radosh joined the party as a teenager, influenced by his parents' commitment to leftist causes. His early life was shaped by the political fervor of the era, and he participated in the New Left movement, particularly opposing the Vietnam War. The revelations during the Khrushchev Thaw in the 1950s, exposing Stalin's atrocities, led him to leave the CPUSA and prompted his disillusionment with communism, ultimately driving his shift toward anti-communist conservatism in the 1970s and 1980s.

Radosh earned his academic credentials with a BA in History from the University of Wisconsin in 1957, an MA from Columbia University in 1959, and a PhD in History from the University of Rochester in 1969. His scholarly work initially examined communist influences in the U.S., as seen in books like 'American Labor and United States Foreign Policy' (1969). Over time, he collaborated professionally with David Horowitz, co-authoring influential works such as 'Divided They Fell: The Demise of the Democratic Party and the Future of the Left' (1996) and 'The Professors: The 101 Most Dangerous Academics in America' (2006). Radosh has been influenced by Horowitz's own transition to conservatism and has contributed to conservative media outlets, writing for publications like The Daily Wire and The Daily Caller (where he is a Contributing Editor), and appearing on platforms that promote anti-communist narratives.

As a social conservative pundit, Radosh has authored over a dozen books, including 'Red Star Over Hollywood: The Film Colony's Long Romance with the Left' (2005) and 'America at the Crossroads: Democracy, Power, and the Neoconservative Legacy' (2006), often exploring the intersections of politics, culture, and ideology. He has taught at institutions like Rutgers University, Hunter College (City University of New York), and the University of Illinois at Chicago, and holds positions as an Adjunct Fellow at the Hudson Institute and a Senior Fellow at the Discovery Institute. He continues to lecture and write, positioning himself as a critic of progressive movements. His personal evolution from a former Marxist activist to a prominent conservative voice underscores themes of ideological realignment in 20th-century American intellectual history, making him a key figure in mapping networks of influence in American political discourse. Notably, his work on the Rosenberg case, including 'The Rosenberg File: A Search for the Truth' (1983), co-authored with Joyce Milton, concluded that Julius Rosenberg was guilty of espionage but Ethel Rosenberg was not, a view that sparked controversy.