The failure of the separation of powers scheme can take three forms. One is a branch claiming for itself powers that are clearly granted exclusively to another, as with President Trump taking money that Congress authorized for one purpose and using it for something else entirely. Another mode of failure is for one or both branches to simply fail to use their authority to check the others when called for, like when Congress failed to challenge President Roosevelt’s executive order interning Japanese-Americans during WWII. Finally, an obvious instance of one branch overstepping its authority can be validated by the courts rather than blocked, as when the Supreme Court absurdly voted to uphold the internment in Korematsu v. United States.
Due to a combination of Republican scheming, Constitutional hardball and hyper-partisanship, we are actually experiencing all three of these failures simultaneously. On the one hand, a sharply divided country characterized by hyper-partisanship means that Congress is incapable of exercising its most important powers over the president. Unless one party captures 67 seats in the Senate while improbably losing the presidency, the president cannot be impeached, and without similar margins in the House, vetoes will almost never be overridden. In and of itself, this is an invitation for the president to exercise what Madison called “overruling influence” over the other branches. Who or what will stop him?