Back in 1800, when Jefferson was elected, there were two political parties, like today. Except these two parties are not the same nor do they represent the same ideas. Adams (Jefferson's predecessor) was part of the Federalist party. Jefferson was part of the Anti-Federalist party. What was the difference? Federalists believed, firstly, in a loose interpretation of the Constitution, they believed in a strong central government with inferior state governments. Anti-Federalists believed the opposite: they believed in a strict interpretation of the Constitution and in a weak federal government. So, when Jefferson took office in 1800, he greatly downsized the federal government and made it weaker. Also, with all the confusion surrounding the election of 1800, the 12th Amendment was ratified, which said that a separate ballot must be cast for President and Vice President.
