Recent events have unnerved many Americans about the political problem of executive power. Though it seems not to bother the vast majority of citizens, there has been at least some recognition in the public conversation that the mere possibility that a personage like Donald Trump could get elected president is precisely why a system of ever‐​expanding executive power, such as ours, is dangerous. But the truth is, this concern has been percolating since September 11, 2001. Both Bush and Obama left the office more powerful than they found it. And that makes perfect sense: if history shows us anything, it’s that war centralizes power — often into the hands of a single person.

But as the 2020 campaign picks up, it showcases that the expansion of executive authority isn’t relegated to war powers. While Trump does his best impression of a 19th century European demagogue, Democrats are promising citizens everything to the sun and back in language that seems to presume god‐​like capacities in the office of the president. Unfortunately, talking points on circumscribing executive power make for an unappealing stump speech.

It is therefore worthwhile to reflect on the reason why America’s political heritage features strenuous efforts to protect against kingly usurpers. The Founding generation looked to Rome for lessons. I was struck by this passage from a book by historians Joseph R. Strayer and Dana C. Munro, a succinct history on the expansion of executive power in ancient Rome:

Rome had once been a republic, ruled by an aristocratic Senate whose power could be checked only by uprisings of the city mob. In the first century B.C. this political system caused so much disorder that the citizens of Rome allowed power to be concentrated in the hands of one man — a boss or a dictator. Octavian, the last of these bosses, became Augustus, the first emperor. His powers, however, were not much greater than those of a strong American president. He was commander of the army and head of the administration; he made policy and proposed laws, but he was supposed to act with the advice of the Senate. Augustus’ successors, however, assumed much more power. Frequent civil wars and the necessity of protecting the frontiers made their military functions more important and decreased the power of the Senate. Then came a long period of anarchy in the middle of the third century. When a strong emperor, Diocletian, finally emerged in 285, the condition of the Empire was so bad that every one acquiesced in his assumption of absolute authority. Diocletian and his successors named all officials and levied taxes at will. They were the supreme judges and court of last appeal of the Empire; they had the power of life and death over every citizen. It was an accepted maxim that “the will of the prince has the force of law, since the Roman people by law have transferred to their prince the full extent of their power and sovereignty.”

Notwithstanding how eerily familiar that all sounds, I’m not convinced that we’re condemned to a similarly despotic fate. But as the political scientist Christopher J. Fettweis has recently pointed out, an added pressure in this direction comes from the fact that the United States, as in the case of Rome, is for all intents and purposes a unipolar power (whatever they say these days about the return of multipolarity). Like Rome at the height of its imperial glory, U.S. power in the international system today is highly asymmetrical. It’s foreign policy is preoccupied not with overcoming existential peril from proximate peer belligerents intent on total war, but with chasing remote (and sometimes imaginary) threats in the distant reaches of the periperhy. Unchecked international power carries some of the same hazards as unchecked power in the domestic realm. Look no further than the Trump administration’s spurious citations of the 2001 and 2002 Authorization for the Use of Military Force to legitimate ongoing, and potentially future, wars across the Middle East. Prudence and the Constitution would seem to obligate Congress to repeal, and not replace, these outdated authorizations.

Luckily, as Fettweis details at length through the example of Roman Emperor Hadrian, leaders always have the choice of retrenching and exercising restraint: “By keeping its threats in proper perspective, the United States could recognise that its security does not demand robust international military action. By restraining itself, the United States could demonstrate to the world that force should be a last resort, even for the strongest, most capable state in history, and thus do more to promote peace than all its misguided attempts at global policing. And it would waste far less blood and treasure in the process.”

Here’s hoping.