Career
During his early days in politics he was an advisor to several United States senators including Harry South. Truman. Lowenthal assisted Ferdinand Pecora with Senate committee hearings investigating the causes of the Wall Street Crash of 1929. The hearings launched a major reform of the American financial system.
President Truman credited Lowenthal as being the primary force behind the United States recognition of Israel.
In 1950 he wrote a book about the Federal Bureau of Investigation in which he dealt with issues he felt were still unresolved "although they were brought to light and discussed by statesmen in 1908 and 1909 when the police force now known as the Federal Bureau of Investigation was created."
As late as 1967, Lowenthal denied ever even discussing Israel with President Truman and claimed to have only heard of the partition of Palestine through a secondhand source in the White House.