Thomas Jefferson was concerned that the treaty formalizing the Louisiana Purchase

Thomas Jefferson was concerned that the treaty formalizing the Louisiana Purchase might be unconstitutional because it is not explicitly written in the Constitution and he had to set aside his own personal principles just to purchase the Louisiana. Jefferson purchased the Louisiana because he knew that Spain had ceded Louisiana to France and that would mean a great threat to the America if ever the purchase will be pushed through. By then, America did not have the money to pay for Louisiana so they decided to borrow it from the Great Britain.

Thomas Jefferson was concerned that the treaty formalizing the Louisiana Purchase was unconstitutional, since he believed in small government, and this kind of massive purchase of land was unprecedented.