President Trump has reacted to the House impeachment inquiry in predictable fashion, angrily denying any wrongdoing, spinning “witch hunt” conspiracies, and viciously attacking his accusers and political rivals, demanding, for example, that House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) be “questioned at the highest level for Fraud & Treason.” On Sunday, he even embraced the suggestion that removing him from office could prompt a “Civil War like fracture.”

His combative response inevitably brings to mind President Andrew Johnson, another famous impeachment target whose contemporaries viewed him as emotionally volatile, publicly coarse and recklessly hostile to presidential and constitutional norms. Despite the many personal and stylistic similarities between the two, the political fallout of a Trump impeachment would be far more dangerous than any before.

The reason lies in how the powers of modern administrative government have become joined to partisanship in a polarized nation. This fusion has turned the contemporary party system into a weapon for the promotion of the president’s agenda and fostered a visceral base of supporters who disdain the virtues of deliberation, compromise and pragmatic government. While Congress must hold Trump accountable as an individual, we also must address these broader systemic flaws that have enabled him to undertake such behavior with impunity in the first place.