During Barack Obama’s presidency, frustration among his supporters at unfulfilled campaign promises became so common that a political scientist coined a name for the phenomenon. These supporters, Dartmouth University’s Brendan Nyhan explained, were suffering from the Green Lantern Theory of the Presidency.
The Obama supporters’ belief was that, just as the superhero Green Lantern could will anything into existence using his power ring, presidents could achieve any policy goal if they simply tried hard enough.
Most of the left has moved on from this cartoonish view of the presidency, but not Donald Trump. In recent weeks, the Republican presidential nominee has promised to do everything from cutting car insurance rates to making in vitro fertilization free. These pledges come after he previously claimed that he would impose across-the-board tariffs on all imports, deport millions of undocumented immigrants, end inflation, end the Ukraine war, repeal and replace the Affordable Care Act and abolish the Department of Education, among a number of other big ideas.
Some of his worst ideas would be entirely within his powers as president.
It’s tempting to view these as all empty promises, especially given how many pledges he didn’t fulfill in his first term. But there’s a risk to being too dismissive of presidential power, too, especially when faced with the prospect of a second Trump term. Some of his worst ideas would be entirely within his powers as president, especially the way the office is currently constructed, while his proposals to help the average American are most likely out of reach.
The key to understanding this is what I call the Aquaman Theory of the Presidency: The commander in chief is all powerful in certain circumstances, like how Aquaman can summon aid from sea creatures underwater, and totally useless in other situations, just as Aquaman isn’t much help in the desert.
Consider tariffs. Trump, who has called himself “a Tariff Man,” has said he would levy a 20% tariff on all imports to encourage domestic manufacturing. Additionally, he recently threatened to impose a 100% tariff on cars made in Mexico and a 200% tariff on John Deere tractors if production is moved to Mexico. These tariffs would drive up costs for consumers, spark retaliatory moves that hurt American businesses and destabilize the global economy.
But could Trump do them? Sure. In this case, Tariff Man is Aquaman on his home turf.
Over the last century, Congress has repeatedly expanded the president’s power to impose tariffs during wartime or for national security or even, some argue, any kind of national emergency. Sen. Rand Paul, R-Ky., has proposed a long-shot bill to limit that power, and some free-market supporters hope the Supreme Court might step in, but Trump would have the advantage in this fight for now.
They might be persuaded to tack on one or two of those new proposals, but Trump wouldn’t have much power to force the issue if they didn’t want to do it.
By contrast, Trump would have to go through Congress to fulfill his off-the-cuff promises to end taxes on tips, overtime and Social Security income. Republicans are already planning to extend the 2017 Trump tax cuts, which disproportionately helped the wealthy at a cost of several trillion dollars. They might be persuaded to tack on one or two of those new proposals, but Trump wouldn’t have much power to force the issue if they didn’t want to do it.
Overall, Trump has broad powers for some of his worst ideas:
The success of some of his other ideas would depend in large part on how Congress and the Supreme Court reacted. For example, Trump has proposed signing an executive order to end birthright citizenship, the post-Civil War guarantee from the 14th Amendment that anyone born on U.S. soil is an American citizen. Would Republicans in Congress stand up to the president and seek to undo that? Would the current Supreme Court reject it as clearly beyond the pale? Or would they both acquiesce, effectively granting the president a power that he does not actually have? Trump would have fewer powers, however, when he needed Congress to act. If he earnestly tried to repeal and replace the Affordable Care Act, for example, he would be unlikely to get any more cooperation from all the lawmakers he’d need to do it than in his last attempt in 2017. And Republicans are certainly not going to rush to make IVF free. In fact, anything more complicated than cutting taxes is likely to run into a legislative brick wall, especially since Trump hasn’t outlined any plans for exactly what he’d do and has little support among the rank and file for these ideas. Not all of this is absolute. Presidents can sometimes get Congress to do their bidding, muscling through key pieces of legislation with combinations of threats and favors. And the current Supreme Court would certainly find some limits on presidential power if they are used by a President Kamala Harris. But if Trump gets a second term, he would have some Aquaman-like powers to do a lot of harm and not a lot of power to do good.
Ryan Teague Beckwith is a newsletter editor for MS NOW. 
