The Congressional nominating caucus is the name for informal meetings in which American congressmen would agree on who to nominate for the Presidency and Vice Presidency from their political party.
The system was introduced after George Washington had announced his retirement upon the end of his second term, when the Democratic-Republican Party, and Federalist Party began contesting elections on a partisan basis. Both parties may have held informal caucuses in 1796 to try to decide on their candidates. After the disorganized electoral voting of 1796, both parties held formal caucuses in 1800 that selected their respective presidential candidates (prior to the ratification of the 12th Amendment in 1804 each party ran two presidential candidates). The Federalists secretly held their caucus in early May, but later made their ticket of President John Adams and Charles Cotesworth Pinckney public. The Democratic-Republicans also secretly met in May, and agreed to equally support Thomas Jefferson and Aaron Burr for president. The Federalists did not hold another caucus after 1800.
In 1804, after the passage of the 12th Amendment, the Democratic-Republicans caucus met again. In a ballot of the caucus, George Clinton defeated John Breckinridge and was nominated as Jefferson's running mate. At the 1808 caucus, supporters of James Madison defeated attempts to nominate Clinton or James Monroe instead of Madison. Clinton was nominated as the vice presidential nominee, but Clinton criticized the legitimacy of the caucus system and both Clinton and Monroe considered running for president. The Federalists meanwhile, held a proto-national convention in New York in 1808, where they nominated Charles Cotesworth Pinckney and Rufus King. In 1812, Madison won unanimous re-nomination by the caucus. However, the Democratic-Republican members of the New York legislature denounced the caucus system as illegitimate, and instead nominated DeWitt Clinton, the nephew of George Clinton. The Federalists held another proto-convention in 1812, there they agreed to support Clinton. Clinton ultimately lost the election, but provided a strong challenge to Madison and won 89 electoral votes.