What ideas did James Madison and his party adopt from the Federalists after the War of 1812?
Since Alexander Hamilton was Secretary of Treasury under George Washington, the Federalists had promoted a powerful and active central government that would unify the nation and especially promote business interests and manufacturing. They proposed a national bank, high tariffs, and other government action to bring this about.
By and large, the Republicans under the leadership of Thomas Jefferson, and to some extent James Madison had emerged as a party in opposition to these developments. But after the War of 1812 ended (in 1815) Madison embraced, at least to some extent, most of these plans. He supported rechartering the National Bank in 1816, which was highly galling to many Republicans. Rechartering the bank was part of Henry Clay's so-called "American System," and Madison supported some of its other aspects, including higher tariffs. He did, however, veto federal funds for the construction of the National Road that would run from Maryland to Pennsylvania, claiming that Congressional appropriation of funds for that purpose was unconstitutional. But Madison and many other so-called "National Republicans" generally supported the project of nation-building (including, in fact, internal improvements like the National Road, which he thought should be done with a constitutional amendment) that accelerated after the war. In doing so, they adopted many of the positions formerly held by the Federalists.