Michael Leib was an American physician and politician from Philadelphia. He served as a surgeon in the Philadelphia Militia during the American Revolutionary War. He served as a Democratic-Republican member of the Pennsylvania House of Representatives three times; from 1795 to 1798, 1806 to 1808 and 1817 to 1818. He served as a member of the United States House of Representatives for Pennsylvania's 2nd congressional district from 1799 to 1803 and for Pennsylvania's 1st congressional district from 1803 to 1806. He served as a member of the United States Senate for Pennsylvania from 1809 to 1814. He also served as a member of the Pennsylvania State Senate for the 1st district from 1818 to 1821.

The Republican Party, retroactively called the Democratic-Republican Party, and also referred to as the Jeffersonian Republican Party among other names, was an American political party founded by Thomas Jefferson and James Madison in the early 1790s that championed liberalism, republicanism, individual liberty, equal rights, decentralization, free markets, free trade, agrarianism, and sympathy with the French Revolution. The party became increasingly dominant after the 1800 elections as the opposing Federalist Party collapsed.