Final answer:
The Embargo Act of 1807 was the most unpopular and least successful policy of President Thomas Jefferson. It was intended to hurt Great Britain and France economically to stop their harassment of American shipping but had little impact on these countries and caused economic hardships in America.
Step-by-step explanation:
The most unpopular and least successful of President Thomas Jefferson’s policies was his Embargo Act of 1807. The Act was intended to worsen the economic situations of Great Britain and France in order to stop their harassment of American shipping. However, the Act had little impact on either country, and American shipping suffered greatly as a result, leading to economic hardship at home. This policy was widely criticized and contributed to Jefferson losing favor with the people.