In 1800, Monroe called out the state militia to suppress Gabriel's Rebellion, a slave rebellion originating on a plantation six miles from the capital of Richmond. Gabriel and 27 other enslaved people who participated were all hanged for treason.[47] As Governor, Monroe secretly worked with President Thomas Jefferson to secure a location where free and enslaved African Americans suspected of "conspiracy, insurgency, Treason, and rebellion" would be permanently banished.
Monroe thought that foreign and Federalist elements had created the Quasi War of 1798–1800, and he strongly supported Thomas Jefferson's candidacy for president in 1800. Federalists were likewise suspicious of Monroe, some viewing him at best as a French dupe and at worst a traitor.[48] With the power to appoint election officials in Virginia, Monroe exercised his influence to help Jefferson win Virginia's presidential electors.[49] He also considered using the Virginia militia to force the outcome in favor of Jefferson.[50] Jefferson won the 1800 election, and he appointed Madison as his Secretary of State. As a member of Jefferson's party and the leader of the largest state in the country, Monroe emerged as one of Jefferson's two most likely successors, alongside Madison.