In 1964, President Lyndon B. Johnson, the successor of John F. Kennedy, signed into law the largest tax cut in U.S. history until 1981, the so-called Kennedy–Johnson tax cut. Many scholars have evaluated it as representative Keynesian tax policy; this article focuses on the effort of the Treasury Department, tax experts such as Stanley S. Surrey and Wilbur D. Mills, the chairman of House Committee on Ways and Means, to reform the federal income tax system comprehensively—making it simpler, fairer, and more equitable—and their defeat by the 1964 tax cut. Through the policymaking and legislative process, the Kennedy administration’s Council Economic Advisers defeated the Treasury and Surrey by domesticating Keynes’s ideas on tax policy. Until the 1964 passage of the tax cut, Mills, with his inconsistent action, abandoned the accomplishment of their ideal tax reform.