The tea party has strong libertarian roots and is a functionally libertarian influence on the Republican Party. Compiling data from local and national polls, as well as dozens of original interviews with tea party members and leaders, we find that the tea party is united on economic issues, but split on the social issues it tends to avoid. Roughly half the tea party is socially conservative, half libertarian — or, fiscally conservative, but socially moderate to liberal. Understanding the tea party’s strong libertarian roots helps explain how the tea party movement has become a functionally libertarian influence on the Republican Party. Most tea partiers have focused on fiscal, not social, issues — cutting spending, ending bailouts, reducing debt, and reforming taxes and entitlements — rather than discussing abortion or gay marriage.