The short answer is, a LOT. The president can:

• Sign bills into law, or reject bills that have passed Congress
• Nominate Cabinet members, other leaders and high-level officials in executive branch agencies, ambassadors to other countries, and federal judges, including Supreme Court justices
  All nominees need to be confirmed by a majority vote in the U.S. Senate before officially getting the job
• Fire the leaders of some executive branch agencies, and some other high-level officials in the executive branch
• Issue Executive Orders
  EOs are rules for the federal government. They tell federal agencies how to carry out laws that are already on the books, and can also be used to change rules and procedures that are not specifically set out in law. (More on the difference between federal laws and executive orders here.)
• Pardon or commute the sentences of people who have been convicted of federal crimes
• Declare a national emergency
  When a national emergency is declared, the president has more power to act quickly when an urgent situation needs to be addressed and Congress can’t act fast enough (but there’s a lot of debate over what exactly presidents are allowed to do with emergency powers, so it’s common for a president’s emergency action to be challenged in court)
• Launch and direct military actions, and order the deployment of troops
• Launch nuclear weapons
• Impose sanctions (these are economic and trade restrictions) on people, companies, organizations, and other countries

Sources: the U.S. Constitution; Harvard Kennedy School on executive orders; the Brennan Center for Justice on the President’s emergency powers; the International Emergency Economic Powers Act; the Nuclear Threat Initiative on the President’s nuclear powers

This is a really complicated question – so complicated, in fact, that there have been centuries of debate about it in the courts. That debate continues to this day, every time a lawsuit is filed to stop the president from doing something because there’s disagreement about whether it’s legal or allowed. President Trump’s mass firings of federal workers and executive branch leaders are a recent example of this, showing the Supreme Court’s ability to expand presidential power with its decisions. Other cases show the limits of the president’s powers, like the recent decision to strike down President Trump’s executive order that tried to restrict birthright citizenship.

That said, there are a few things most courts and legal scholars generally agree the president can’t do:

• Declare war
  According to the Constitution, only Congress can declare war on another country. But the president can launch military operations and respond if the U.S. is attacked, so this get complicated and there have been a lot of debates about it.
• Stop the government from spending money that is authorized by Congress (sort-of)
  The U.S. Constitution gives Congress the ‘power of the purse,’ which is the power to decide how the federal government spends its money. If Congress has passed a law or budget specifically requiring money to be spent in a certain way, the president is generally not allowed to stop it from happening, but the president can ask Congress to pass another law making cuts – there’s a process for that called rescission. But recently, the Supreme Court gave President Trump more power to withhold funds without even going through this process – another example of the debate over presidential power changing in real time.
• Fire federal judges, including Supreme Court justices
  Once a federal judge takes office, they can only be removed by being impeached by Congress. This rule exists to protect judges from political pressure and allow them to make decisions more independently.
• Force states to change their laws or policies
  The president is in charge of the executive branch of the federal government, so they don’t have direct authority over state governments. As long as a state law or policy isn’t in conflict with federal law or the U.S. Constitution, the president can’t force changes just because they disagree with what the state government is doing. But they can order the Justice Department to challenge the law or policy in court, investigate it in another way, or use political pressure to try to convince the state to change course.
• Pardon or commute the sentences of people who have been convicted of state crimes
  Because the president is in charge of the federal government, their pardon power only applies to federal crimes.

Sources: the U.S. Constitution; the National Constitution Center on the President’s war powers; the Bipartisan Policy Center on the required process for canceling funding approved by Congress

In the U.S., a president can only be removed from office through impeachment. According to the constitution, a president can be impeached if they are guilty of “high crimes and misdemeanors,” which basically means serious misconduct, including (but not limited to) crimes committed while in office.

Impeachment is a multi-step process that happens in Congress.

• Usually, there’s an impeachment inquiry – this is an investigation to gather evidence and figure out if the misconduct is serious enough that impeachment is warranted
• A U.S. Representative, or group of representatives, introduces articles of impeachment, which lay out what the president has been accused of doing, and the whole House of Representatives votes. If a majority (more than half) vote yes, then the president has officially been impeached – but that’s not the end of the process. This part is like being charged with a crime.
• The final step is the impeachment trial, and that happens in the U.S. Senate. It’s set up basically like a criminal trial. The Chief Justice of the Supreme Court serves as the presiding officer or ‘judge’ and can make rulings on things like the admission of evidence, and teams of representatives from the House serve as the prosecution and defense. Senators can subpoena witnesses and ask questions of the prosecution and defense teams. At the end of the trial, the Senate acts as a jury and votes on whether to remove the president from office. 
• If a two-thirds majority of the Senate votes yes (67 yes votes out of 100), the president is immediately removed from office, and the vice-president becomes president. (Or, if for some reason the vice-president can’t serve, the official who is next in the line of succession becomes president instead – more on that below.)
• If the president is removed, the Senate can hold another vote on whether to ban the president from holding elected office in the future. This vote only needs a simple majority (51 out of 100), not two-thirds.

Impeachment and removal are not the same thing as being convicted of a crime, so a President could still potentially be prosecuted for crimes committed while in office after being removed. Vice-presidents, Supreme Court justices, and other executive officials like Cabinet members can also be removed from office using the impeachment process.

Impeachment has been very rare in the U.S. so far – only three presidents have been impeached, and none have been removed from office. 

Sources: the U.S. Constitution; 2019 Congressional report on impeachment investigations

The constitution has a plan for that! 

There are several officials who are in the line of succession to the presidency, meaning they would serve if the president (or others above them in the line) could no longer serve. Succession would happen if a president is impeached, but also if a president dies, resigns, or is not able to do the job for any other reason. This has only happened a few times in U.S. history. 

The line of succession is:

1. Vice-President
2. Speaker of the House (the leader of the House of Representatives)
3. President Pro Tempore of the Senate (the leader of the Senate)
4. Secretary of State
5. Secretary of the Treasury
6. Secretary of Defense
7. Attorney General
8. Secretary of the Interior
9. Secretary of Agriculture
10. Secretary of Commerce
11. Secretary of Labor
12. Secretary of Health and Human Services
13. Secretary of Housing and Urban Development
14. Secretary of Transportation
15. Secretary of Energy
16. Secretary of Education
17. Secretary of Veterans Affairs
18. Secretary of Homeland Security

Sources: the U.S. Constitution; the full line of succession according to the Presidential Succession Act of 1947

Here’s something unique about the U.S. system – unlike most other democracies, we don’t choose our highest elected official directly with a popular vote. So even though every voter gets to vote for President, we don’t vote directly for our chosen candidate. Instead, we have the Electoral College. The Electoral College is made up of 538 electors – one for every U.S. Representative (435) and U.S. Senator (100) in every state, plus three electors representing Washington DC, bringing the total to 538. Each elector gets one vote in the Electoral College.

Electors are not just votes – they are actual people who meet in person to cast those votes! Each presidential candidate has electors in every state where they’re on the ballot. Electors are usually required by law to vote for the candidate who won their state – if they don’t, they can be fined, replaced by someone else, or even charged with a crime.

What happens on and after election night? 

• In every state and Washington DC, all the votes are counted (sometimes this takes several days)
• In 48 states and Washington DC, whichever candidate gets the most votes in that state receives all of that state’s electoral votes – this is known as winner-take-all
• In Maine and Nebraska, electoral votes are awarded semi-proportionally: two electoral votes are awarded to whoever gets the most votes in the state, and the rest of the state’s electoral votes are awarded to whoever gets the most votes in each separate Congressional district.
  Here’s an example: in 2008, John McCain won the most votes in Nebraska overall, but Barack Obama won the most votes in Nebraska’s 2nd Congressional district – so President Obama got 1 of Nebraska’s electoral votes and John McCain got the rest.
• A candidate needs 270 electoral votes to win the presidency – whoever gets at least 270 is the winner.
• In each state, the winning candidate’s electors are sent to a meeting in December to officially cast the state’s electoral votes.
• On January 6 of the following year, Congress meets and formally certifies the Electoral College votes – this is the part that makes the results official and final
• On January 20, the new president is inaugurated and takes office

Because we use the Electoral College process, it’s possible for a candidate to win the national popular vote and still lose the election – the last time this happened was in 2016.

What if nobody gets to 270?

If no candidate gets 270 electoral votes, or if there’s a tie, the election goes to the U.S. House of Representatives and the 435 Representatives vote for President. This has only happened twice – the last time was 200 years ago.

How do other countries do it?

Lots of different ways! The Pew Research Center has a great explainer if you’re interested in learning more. 

Sources: the U.S. Constitution; the National Archives

The president can do a lot with an executive order, but their power is not unlimited. Sometimes an order is blocked by a court for being illegal or unconstitutional; sometimes Congress passes a law to stop an order; and sometimes, despite the government’s best efforts, there are logistical or diplomatic hurdles that can’t be overcome.

When President Obama was elected in 2008, he pledged to close Guantanamo Bay, the military prison established in Cuba by President George W. Bush in 2002 to hold people suspected of or charged with terrorism. Many of the detainees had been held for years without charges (in what human rights groups agreed was a violation of international law), and subjected to torture and abuse. The cases of detainees who were charged with crimes were under the jurisdiction of the military justice system, which moves much more slowly and has less oversight than the civilian system that most of us are more familiar with. On his third day in office, President Obama signed two executive orders directing the government to review the cases of everyone detained at Guantanamo, figure how and where to transfer them, and close the prison in no more than a year. 

That goal stalled when it became clear that closing Guantanamo Bay would probably mean transferring some detainees to the U.S. Members of Congress from both parties were against that, and others opposed transferring the detainees to other countries for national security reasons. The Obama administration succeeded in moving some detainees out of Guantanamo, but opposition continued – in 2015 Congress even passed a bill to prevent more transfers. Meanwhile, military cases moved extremely slowly and the government needed to negotiate with the other countries who were potentially willing to take detainees. By the end of the Obama administration, 41 people were detained there. As of January 2025, there were still 15 detainees, including 3 who were approved for release and 3 in “indefinite detention” who have not been charged with any crimes.

Sources: White House Archives of President Barack Obama; Amnesty International USA; the US Department of Justice; the New York Times; Reuters; PBS