It's the season to make big promises. With the presidential election fast approaching, candidates Hillary Clinton and Donald Trump are pledging to lift the middle class, revive the economy and restore the United States' position in the world, among a slew of more technical policy plans.

Obviously, some of these proposals will be easier to fulfill than others. There are some areas in which the U.S. president can act almost unilaterally, and others that lie almost entirely out of the president's control. But for voters who haven't taken a civics class in years, it may be hard to distinguish one from the other.

So which election promises is your candidate actually likely to keep? Bernadette Meyler, a constitutional scholar at Stanford Law School, weighed in.

This interview has been edited for length and clarity.

How much power does the president really have? Do people believe there’s more power in the office than there really is?

People definitely imagine the president has more authority than he or she actually does. At the same time, we’re at a particular moment when whoever is elected president may wind up having more power than a normal president would. That's partly because the Supreme Court still has a vacancy from this past term, when Justice Scalia passed away, and there was a failure to confirm a new justice.

The Supreme Court, which is usually the final check on a lot of executive action, is not exercising its functions in a normal way right now. We see this with a decision like the United States vs. Texas, where the court was split 4-4. In the case of the Supreme Court being equally divided, the lower court opinion is just affirmed.

So, first of all, appointing a new Supreme Court justice would be a large exercise of power for the new president. And then even in the absence of the confirmation of someone new, if the Supreme Court isn’t operating normally, that might give the president more latitude.

What are other areas in which a president really does exercise power?

One is negotiating treaties, but, of course, treaties have to be confirmed by the Senate. Now, presidents can withdraw from treaties and trade agreements more unilaterally. So when you hear Trump talking about getting out of the Trans Pacific Partnership or renegotiating NAFTA, that might be within a president’s power.

Some of the president’s powers with respect to foreign affairs are broader than some of the domestic powers. Even though Congress is supposed to declare war, in general, many presidents have led military interventions without congressional approval.

Another set of powers that are quite broad is clemency, of pardoning or curtailing sentences. So one of Clinton’s issues has been trying to diminish the racial effects of mass incarceration. Clemency might be one tool in that struggle.

The president also has a fair amount of power with the administrative state, for example, setting the direction for the Environmental Protection Agency. The president could probably do a fair amount to implement something like the Paris agreement on climate change. Or if Trump were elected, he could withdraw from the Paris agreement.

Conversely, are there policy proposals that are likely over-promises, where the president doesn’t really exercise that much influence?

Yes. One is the set of issues that depend on the courts. So Clinton has proposed both campaign finance reform and more gun control measures. Both of those depend on the judiciary’s construction of the First Amendment with campaign finance and the Second Amendment with gun control.

Some of what Trump has said on immigration would encounter constitutional problems in the courts. At some point, he was proposing that we would use restrictions on aliens’ transfer of funds outside of the country to force Mexico to pay for a wall. People have pointed out other practical problems with the plan, but there is also an equal protection argument against targeting aliens. Even if they are not citizens, once someone is in the country they still have certain rights to equal protection and due process under the 14th Amendment.

Another area that might be more difficult is tax reform. Clinton has said that she wants to create a fairer tax system for the wealthy, but tax reform still has to originate in the House. It requires congressional approval. So we could see a stalemate on that front.

Similarly, the president would need congressional approval to reform the Affordable Care Act. If you were to assume the Congress that we have right now, a lot of Clinton’s proposals would be difficult to implement. Given the antipathy that this Congress has expressed toward the Affordable Care Act, I think Trump’s proposals would be more likely to get through.

Tax plans are often a huge part of presidential platforms. How often are those plans put into action? Is it rare that a candidate is able to make tax changes they talk about?

It is rare, and it depends on the agreement of Congress. Historically, Congress has been more likely to approve changes in the direction of giving more exemptions for the wealthy rather than the opposite direction. It’s difficult to get past the effect of lobbying on Congress with respect to tax provisions.

So the main forces that constrain a president’s power are what you learned in civics class, the other branches of the government?

Definitely. There are also proposals that might require state approval, like some of Clinton’s efforts to protect labor, or efforts to incentivize states to enact the Medicare sections of the Affordable Care Act. A lot of latitude on education reform is left to the states as well.

Do you think the candidates are aware of what their limitations in office will be? With many presidents, do we see a learning experience, where they come in with ambitious plans and find themselves stymied?

Yes. Obama, for example, had a much-too rosy vision of how much he could get done with the collaboration of Congress.

I think Clinton would be less likely to have an unrealistic view of what she could accomplish, because of her experience as secretary of state and first lady. I don’t think Trump is as familiar with the constitutional limitations, and also hasn’t been in a position where he has to negotiate with Congress. He’s already had to ratchet back on various proposals that have hit constitutional or congressional obstacles.

But at the same time, if we assume that the general orientation of Congress would remain constant, a lot of his proposals would be less likely to meet with congressional disapproval than Clinton’s.

Is it harmful to make these campaign promises that the president can’t really keep?

I think it is. First, it’s harmful if they are promises that have constitutional limits. It seems disingenuous to make promises knowing it would be almost impossible to implement them unless the Constitution is altered in its interpretation or an amendment is passed, unless you are advocating for an amendment. The other harm is the candidate may be focusing their energy on something that is impossible to deliver, rather than something that might be more easily accomplished.

If the president has less power than people assume, are we overestimating the importance of the election? 

I would say not in this instance, because one effect of the president is on the standing of the country in the international community. One of the areas where the president’s power is more pronounced is in foreign affairs. To the extent that internationally there is a very different view of the candidates and who they would be sympathetic to, that actually might have more impact.

Some scholars have argued that the office of the president is gradually becoming more powerful. Do you agree?

Certainly presidents are acting without congressional approval more than previously in certain areas, like entering into war abroad. But at the same time, the president’s power has become a lot more limited because of congressional gridlock. One of the main ways in which presidents traditionally exercised power was proposing a platform that would be implemented through legislation and executive action, and forging coalitions to push legislation through. That’s become so challenging that that very traditional way of exercising power has become closed off in many respects.

To the extent that we see more executive action outside of the legislative process, often that’s a way of circumventing this gridlock. I couldn’t say whether the president is more powerful than he used to be — certainly there are arguments on both sides — but I think the nature of presidential power has shifted to circumvent some of these blockages in the legislative process.

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