Heller was a leading American economist of the 1960s, and an influential advisor to John F. Kennedy as chairman of the Council of Economic Advisors, 1961-64. He was a Keynesian who promoted cuts in the marginal federal income tax rates. This tax cut, which was passed by Lyndon B. Johnson and Congress after Kennedy's death, was credited for boosting the U.S. economy. Heller developed the first "voluntary" wage-price guidelines. When the steel industry failed to follow them, it was publicly attacked by Kennedy and quickly complied. Heller was one of the first to emphasize that tax deductions and tax preferences narrowed the income tax base, thus requiring, for a given amount of revenue, higher marginal tax rates.
The historic tax cut and its positive effect on the economy has often been cited as motivation for more recent tax cuts by Republicans.
The day after John F. Kennedy was assassinated, Heller met with Lyndon Johnson in the oval office. To get the country going again, Heller suggested a major initiative he called the "War on Poverty", which Johnson adopted enthusiastically. Later, when Johnson insisted on escalating the Vietnam war without raising taxes, setting the stage for an inflationary spiral, Heller resigned.
In the early phases of his career, Heller contributed to the construction of the Marshall Plan of 1947, and was instrumental in re-establishing the German currency following World War II, which helped usher an economic boom in West Germany.
Heller was critical of Milton Friedman's followers and labelled them cultish: "Some of them are Friedmanly, some Friedmanian, some Friedmanesque, some Friedmanic and some Friedmaniacs.