"Upon being elected, I will give the United States Congress a hundred days to get their act together and have the courage to pass reasonable gun safety laws," Sen. Kamala Harris (D-Calif.) said Monday evening on CNN. "And if they fail to do it," the Democratic presidential candidate continued, "I will take executive action."

The details of her gun control plan are irrelevant here. Suffice it to say they’ll appeal to the average Democrat — her town hall crowd gave a hearty round of applause — and garner rather less enthusiasm from most Republicans. But what shouldn't draw anyone's support, regardless of party affiliation or views on gun rights, is this 100-day ultimatum. It turns on a fundamental misconception of the nature of executive power in America — the same misconception, in fact, that President Trump has exploited to contemptible ends.

The president is not supposed to be a policymaker. I know, I know, we usually conceive of a responsible voter as one who sifts candidates based on their platforms, not lesser considerations like personality or whether it'd be enjoyable to drink a beer in their company. And that's right, to a point. Certainly, a president's ideas matter and will shape the direction of the country during their tenure in office. That's especially so for foreign policy, where the president's constitutional role as commander in chief affords considerable say-so in the conduct and conclusion of ongoing wars, of which we have many.

Likewise, executive discretion means the president has some (legally vague and disputable) leeway in how to enforce the law, and the sheer number of rules on the books at this point necessitates limited enforcement priorities: "The reach of federal law has grown so vast that no administration can target more than a small percentage of violations, thereby unavoidably giving the president broad discretion," explains Ilya Somin, a law professor at George Mason University.

But the presidency is nevertheless designed as an administrative position. Congress creates policy, and the president administers it. The legislative branch legislates, and the executive branch executes.

So yes, the president's policy commitments are important, but it's not because the president is a formal source of policy. If a president has been in office 100 days and Congress has declined to pass legislation as he or she desires, there's not a lot to be done. The Constitution doesn't have an ultimatum clause. There's no 100-day timer which, once triggered, buzzes lawmaking power over to the White House.

Even when Congress makes the president very unhappy, the balance of powers does not change. Even when Congress makes the people very unhappy, the balance of powers does not change. If we don't like what Congress is doing (or not doing), the solution is to get a different Congress. It is not to shrug our shoulders and let the president rule by fiat.

And it shouldn't have to be said, but that's so whether we have a President Harris or a President Trump, whether the policy problem at hand is gun rights and regulations or, say, constructing an expensive and useless wall on our southern border. Indeed, the plan Harris outlined Monday is a Democratic version of Trump's border wall national emergency, equally blatant in its intent to ride roughshod over constitutional separation of powers should Congress decline to act as the president wants.

As a senator, Harris should recognize the problem with this approach. A February statement from her Senate office about Trump's revealingly lackadaisical emergency declaration decried it as a "ridiculous" effort "to circumvent the authority of Congress ... to pay for the president's vanity project." Now, as a presidential candidate, these scruples are nowhere to be found. "I could do the gun reform over a longer period of time," she could say of her ultimatum, in paraphrase of Trump on his emergency. "I didn't need to do this. But I would rather do it much faster."

This functional concentration of power in the president — any president — may seem convenient, even "inspiring," when wielded by a politician you like in service of policies you support. But the danger here should be obvious with just a little foresight: That politician will not be in office forever, and soon a very different president will wield that power for a very different purpose.

The expansions of executive authority under the Bush and Obama administrations presented Trump with a "turnkey tyranny," and Trump's end-runs around Congress will in turn set precedent a future Democratic president like Harris will similarly abuse.

And absent major structural reform, we will be stuck in this cycle forever, governed not by a balance of ambition tempering ambition but by the increasingly unfettered choices of a single person holding far more power than any human ought to have. This spiral toward authoritarianism may not be inevitable, but that significant portions of the population are myopic enough to cheer its progress in Harris while condemning it in Trump — and vice versa — does not give me much hope.