Final answer:
President Richard Nixon originated the thinking that led to New Federalism, but it was under President Ronald Reagan's administration that the most significant changes associated with New Federalism were made.
Step-by-step explanation:
The original thinking for New Federalism, which emphasizes the transfer of certain powers from the federal government back to the states, began under President Nixon. However, it was under the administration of President Ronald Reagan that the most significant changes associated with New Federalism were made. Reagan's devolution revolution sought to restore state prominence in policy areas and provide more administrative efficiency by decentralizing policies. Despite his efforts, Reagan faced opposition which led to an inconsistent track record in promoting New Federalism policies and initiatives.