The Biden administration has signalled an ambitious legislative agenda, including plans to reform immigration, stimulate the economy and strengthen the federal Covid-19 response. Biden, who was a senator for most of his political career, respects Congress and has emphasized the importance of acting through it. During the presidential campaign, he was not shy about criticizing then-President Donald Trump for abusing his executive authority.

Biden is not alone: Many Democrats think that a lesson of the Trump years, culminating in the siege of the Capitol, is that presidential power needs to be curtailed. Power that has accreted to the presidency over the years should be transferred back to Congress. Executive branch agencies, above all the Justice Department, should enjoy more autonomy. Oversight of the presidency should be strengthened. Only with such reforms can we be sure that future presidents will not abuse their powers.

This discomfort with the “imperial presidency,” as the historian Arthur Schlesinger Jr. called it, is not new. Liberals have worried about an excessively powerful presidency since at least Richard Nixon.

But Democrats should be careful what they wish for. While undoubtedly many reforms of the presidency are overdue — including elements of the Protecting Our Democracy Act, which would increase congressional oversight and reduce conflicts of interest — a weakened presidency would hamper national governance, and Democratic policies in particular.

Consider, for example, climate regulation. When the Democrats controlled the presidency and both houses of Congress in 2009, the American Clean Energy and Security Act (also called the Waxman-Markey bill), which would have reduced greenhouse gas emissions, was blocked by the Senate. Yet a great deal of progress was made on climate regulation during President Barack Obama’s terms. The reason is that he unilaterally implemented climate regulations, drawing largely on authority to regulate pollution granted to the Environmental Protection Agency by the Clean Air Act of 1970. Biden will want to advance the climate agenda by expanding and strengthening these regulations.

Another urgent issue is immigration. In 2010, Congress debated the Dream Act, which would have granted legal status to people who entered the country illegally as children. Again, the Senate blocked the bill.

Obama subsequently granted protections to so-called Dreamers, using his unilateral authority under the immigration laws. Biden has proposed an ambitious immigration reform to Congress, but legislation might take months or years — or, as has happened so often, it might never pass. He is using his unilateral authority to reverse the travel ban against certain countries and other Trump-era executive actions that burdened undocumented immigrants and other foreigners, but if legislation fails, he might do more with his executive authority to make progress on his immigration goals.

Obama enjoyed two major legislative successes: the Dodd-Frank Act, which strengthened financial regulation, and the Affordable Care Act, which subsidized health insurance. But when changes were needed for both laws to correct technical errors, Congress balked. Obama kept the laws alive through unilateral actions, some of them on the boundary of legality.

True, when Trump took power, he reversed some of Obama’s unilateral actions, causing damage to the environment, the immigration system, health insurance and financial regulation. He also used his unilateral powers to unleash a destructive trade war. But the point is that now, with Biden in the Oval Office, it will be difficult — if not impossible — to reverse Trump’s reversals unless Biden has the same powers to engage in unilateral action that Trump, Obama and earlier presidents enjoyed.

Liberals also complain there are too many emergency statutes, which give the president enhanced powers to implement programs based on a declaration of emergency that is mostly unreviewable by courts. And yet a major complaint against Trump was that he failed to fully use his emergency powers to address the Covid-19 pandemic; he could have, for example, increased restrictions on movement to help curtail the contagion and done more to help states buy protective equipment and to distribute vaccines. For Biden to follow through on his plan to formulate a more aggressive response to the pandemic, he will need to rely on the emergency powers that Trump disregarded. Biden will accomplish little if he cannot use the president’s traditional unilateral powers to the same extent that Trump did. The Democratic margin in the Senate — zero — is too slim for Biden to push ambitious laws through Congress, which is balky and slow even when majorities in both houses are broadly in agreement with the president.

But of even greater significance, Democrats should understand that because of the structure of the U.S. constitutional system, they benefit from a powerful presidency more than Republicans do. It’s not just that Congress by its nature moves slowly and gets little done, which often suits Republicans just fine, as they tend to prefer the status quo.

Congressional approval requires the consent of the Senate, which is disproportionately influenced by conservative senators from largely rural states. If power is moved from the presidency back to Congress, national policy will shift to the right, on average, over time.

A possible lesson of the Trump years is that the risk of abuse by the president is so great that the presidency should be stripped of powers even if that means that the U.S. government will be permanently impaired.

If this is true, Democrats who plan to act on this view should prepare themselves for a diminished national government that will be unable to solve the country’s most pressing problems. Biden, who signed 17 executive orders and other directives in his first day of office, seems to be aware of this.