For more than half a century, historians have relied (often implicitly) on a model of organizing U.S. political history around distinct and separate “party systems,” pitting two competitive, stable, national parties against one another for long stretches of time between short bursts of realignment. In the context of the shifting political landscape of 1868, however, explaining the partisan politics of the Johnson impeachment through the party system model is the equivalent of forcing a square peg into a round hole.

How, then, are we to understand the partisan breakdown of the 1868 vote to impeach? If we conflate the Union Party with the Republican Party, was Johnson a Republican? He may have flirted with the Democrats in pursuing a revived Union Party, but he was not a Democrat. And while Democrats certainly supported Johnson’s vision for Reconstruction over that of the Republicans, they did not view him as a member of their party either. In other words, including Johnson in any kind of accounting of the partisan politics of impeachments is confusing at best.

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We argue that it is high time to shed the confines of that model. Nineteenth-century politics are better described as fluid, unstable, and federal, operating through a series of mechanisms—networks, newspapers, customs, and laws—unique to that era. Political actors used these mechanisms to address the most pressing ideological and constitutional conflicts of their era, often in concert with broader political activism. They could quickly organize new parties to address problems as they arose, and just as quickly discard parties when the issues were resolved (or when absorbed by another party). In this way, parties were deeply integrated into the broader fabric of American political life, rather than serving as its organizing structures.