Wide consensus exists that the Tea Party influenced the Republican Party. Exactly what those effects were, and how they were achieved is less clear. This chapter examines how the Tea Party disrupted the US political process between 2010 and 2018. Using granular spatiotemporal information on Tea Party activism, we analyze the insurgency’s impact on the Republican primaries for the 2010 election, the 2010 general election, and the aftermath. Our results show that the number of Tea Party protests in a congressional district predicted the number of subsequent primary challengers, and that the number of local Tea Party groups in a district predicted who won. We further examine the emergence in 2010 of the Tea Party Caucus in the House of Representatives, which institutionalized the insurgency’s influence in Congress. Of the 71 politicians who joined the Caucus, just 23 remained in the House by 2018. Despite the declining influence of the Tea Party on the streets and in government, its activism appears to have increased radicalization within the Republican Party. We conclude that the Tea Party served as a congressional watchdog, successfully keeping Republicans acting in line with its goals.