When the makers of “Schoolhouse Rock” set out in the 1970s to explain how the federal government works, they likened it to a three-ring circus. It was more than just a comment on the chaos of Washington — it was a metaphor for the three coequal branches of government that make our democracy what it is.

“Each controls the other, you see,” the song went, “and that’s what we call checks and balances.”

I’m an investigative reporter for The New York Times, and I’ve been thinking a lot about how those three branches — the basic building blocks of government — will fare with President-elect Donald Trump returning to power. He has promised to upend the system and use its power to prosecute his political enemies, and Democrats and anti-Trump Republicans warn that means he will use his second presidency to rule like an autocrat, putting extraordinary pressure on the nation’s democratic experiment.

Some people I have spoken to about this, including top officials from Trump’s first administration, have faith in the three branches of government, a system built to keep presidents’ power in check.

But the country’s three branches of government are in a weaker position to hold a president accountable than they were when Trump first took office in 2017, in part because of the stranglehold he has over his own party. And some of the change he has promised to bring to Washington would only further erode checks and balances.

“He’s enjoying unified government but, just as importantly, the party itself has been remade in his image,” said William Howell, the dean of the new Johns Hopkins School of Government and Policy in Washington.

A matter of civics

The founders wrote the Constitution purposely to prevent any single person from amassing too much power. To do this, they set up three branches of government intended not just to check each other, but to be rivals for power.

Over American history, even as the United States became a world power, the Constitution has shown remarkable resilience. No dictator seized power, the country survived a Civil War and presidents from varying political parties peacefully handed the reins of government to each other.

“In a nation of immigrants, it’s what binds us together,” said Howell, who has studied and written about the separation of powers and how populism threatens the American government. “Most Americans look upon the Constitution in the same way they would look upon scripture, and the defining feature of the Constitution is the separation of powers and checks and balances.”

One of the greatest tests of the three branches came when President Richard Nixon was accused of abusing his power and breaking the law. He was investigated by the Justice Department and F.B.I. in the executive branch. He was compelled to disclose evidence in a landmark decision by the Supreme Court, which is part of the judicial branch. And he ultimately resigned once he believed he would be impeached in Congress, or the legislative branch.

Several presidents since, including President Bill Clinton, President Biden and Trump himself, were also investigated by the government they led. But as Trump approaches his second term, he has made it clear that he does not want any branch of government to rival his power.

A willingness to push the boundaries

During Trump’s first term, aides who served as guardrails often tried to restrain him by telling him that something was potentially illegal or just plain wrong. Sometimes that worked. But sometimes his actions created questions about whether he broke the law, leading the Justice Department to investigate him.

As a presidential candidate and now as the president-elect, Trump has signaled that he has learned from the experience of having Justice Department appointees who were willing to investigate him — and has put loyalty to him above all other traits for his second-term appointees in the executive branch.

He says he will appoint his own defense lawyers who represented him in a criminal case to top Justice Department positions, including deputy attorney general. He also said he would nominate Kash Patel, an extremist from his first administration who built his political brand on repeatedly attacking the Justice Department and F.B.I., to lead the F.B.I.

Trump also faces fewer potential obstacles from the judicial branch.

When he took office in 2017, the ideological divide was evenly split on the Supreme Court. But over his term, he appointed three justices and stacked the lower courts with hardened conservatives. Earlier this year, in connection with the Justice Department’s indictment against him for his role in the Jan. 6, 2021, attack on the Capitol, the court ruled that a president has significant immunity when taking official acts. Trump embraced the decision as meaning he is “immune from all of the stuff that they charged me with,” saying in a news conference at his New Jersey golf club in August that he views himself as liberated from criminal exposure.

The last check that remains is Congress.

House Democrats impeached Trump twice for his conduct during his first term, and the Senate declined to convict him both times. Republicans now control both houses of Congress, as they did when he took office in 2017. But the Republican Party of today is far more supportive of Trump than it was at the beginning of his first term, when the Senate was stocked with Trump critics and moderates like Senator John McCain, who died in 2018, or former Senator Jeff Flake of Arizona, who decided not to run for re-election that year.

The first test

As my colleague Carl Hulse recently pointed out, one of the first tests of the checks and balances — and whether any of the three branches are still willing to jostle for power — will play out with Trump’s cabinet appointments.

It’s the job of the Senate to decide whether or not to confirm a president’s cabinet nominees, a process known as “advice and consent.” But Trump has demanded that the Senate surrender its role in vetting his nominees if its members are unwilling to give him the people he wants, and allow him to confirm them himself through recess appointments instead.

Previous presidents have made recess appointments. But what would be different this time is that Trump would be making recess appointments for nominees who under previous presidents would be considered all but un-confirmable because of their checkered histories and views.

The Senate — and the newly elected majority leader, John Thune — will have to grapple with appointments of controversial figures like Tulsi Gabbard, Pete Hegseth and Robert F. Kennedy Jr., knowing that if members move to reject them it could set off one of the first fights over checks and balances.

Howell said this all leaves the American people as the ultimate line of defense.

“Sitting behind all this is the public that, through elections and protests and public opinion, can determine who is president and the pressures put on them when they are in office,” he said.