Named after Amerigo Vespucci, an Italian explorer who helped out the then revolutionary concept that the lands that Christopher Columbus sailed to in 1492 were part of a diffrent continent.
The Anti-Federalists believed in a "loose" interpretation of the Constitution, since they wanted the Federal Government to have more control over the individual states, meaning that they wanted the powers that were not explicitly stated in the Constitution to go the federal government.
Offered his asstiance to help defeat them if they didn't accept