On Monday, Mark Meadows, a former White House chief of staff, testified in an effort to move the Georgia racketeering case against his former boss Donald Trump and co-defendants to federal court. On the stand, he said that he believed his actions regarding the 2020 election fell within the scope of his job as a federal official.The courts will sort out his legal fate in this and other matters. If convicted and sentenced to prison, Mr. Meadows would be the second White House chief of staff, after Richard Nixon’s infamous H.R. Haldeman, to serve jail time.But as a cautionary tale for American democracy and the conduct of its executive branch, Mr. Meadows is in a league of his own. By the standards of previous chiefs of staff, he was a uniquely dangerous failure — and he embodies a warning about the perils of a potential second Trump term.Historically, a White House chief of staff is many things: the president’s gatekeeper, confidant, honest broker of information, “javelin catcher” and the person who oversees the execution of his agenda.But the chief’s most important duty is to tell the president hard truths.President Dwight Eisenhower’s Sherman Adams, a gruff, no-nonsense gatekeeper, was so famous for giving unvarnished advice that he was known as the “Abominable No Man.” In sharp contrast, when it came to Mr. Trump’s myriad schemes, Mr. Meadows was the Abominable Yes Man.It was Mr. Meadows’s critical failure to tell the president what he didn’t want to hear that helped lead to the country’s greatest political scandal, and his own precipitous fall.Donald Rumsfeld, who served as a chief of staff to Gerald Ford, understood the importance of talking to the boss “with the bark off.” The White House chief of staff “is the one person besides his wife,” he explained, “who can look him right in the eye and say, ‘this is not right. You simply can’t go down that road. Believe me, it’s not going to work.’” A good chief is on guard for even the appearance of impropriety. Mr. Rumsfeld once forbade President Ford to attend a birthday party for the Democratic majority leader Tip O’Neill because it was being hosted by a foreign lobbyist with a checkered reputation.There used to be stiff competition for the title of history’s worst White House chief of staff. Mr. Eisenhower’s chief Adams was driven from the job by a scandal involving a vicuna coat; Mr. Nixon’s Haldeman served 18 months in prison for perjury, conspiracy and obstruction of justice in the Watergate scandal; and George H.W. Bush’s John Sununu resigned under fire after using government transportation on personal trips.But the crimes Mr. Meadows is accused of are orders of magnitude greater than those of his predecessors. Even Mr. Haldeman’s transgressions pale in comparison. Mr. Nixon’s chief covered up a botched attempt to bug the headquarters of the political opposition. Mr. Meadows is charged with racketeering — for his participation in a shakedown of a state official for nonexistent votes — and soliciting a violation of an oath by a public officer.Mr. Meadows didn’t just act as a doormat to President Trump; he seemed to let everyone have his or her way. Even as he tried to help Mr. Trump remain in office, Mr. Meadows agreed to give a deputy chief of staff, Chris Liddell, the go-ahead to carry out a stealth transition of power to Joe Biden. This made no sense, but it was just the way Mr. Meadows rolled. Mr. Trump’s chief is a world-class glad-hander and charmer.As part of the efforts to subvert the 2020 election, Mr. Meadows paraded a cast of incompetent bootlickers into the Oval Office. This culminated in a wild meeting on the night of Dec. 18, 2020 — when Mr. Trump apparently considered ordering the U.S. military to seize state voting machines before backing down. (Even his servile sidekick Rudy Giuliani objected.) A few days later, Mr. Meadows traveled to Cobb County, Ga., where he tried to talk his way into an election audit meeting he had no right to attend, only to be barred at the door.All the while, the indictment shows that Mr. Meadows was sharing lighthearted remarks about claims of widespread voter fraud. In an exchange of texts, Mr. Meadows told the White House lawyer Eric Herschmann that his son had been unable to find more than “12 obituaries and 6 other possibles” (dead Biden voters). Referring to Mr. Giuliani, Mr. Herschmann replied sarcastically: “That sounds more like it. Maybe he can help Rudy find the other 10k?” Mr. Meadows responded: “LOL.”Mr. Meadows’s testimony this week that his actions were just part of his duties as White House chief of staff is a total misrepresentation of the position. In fact, an empowered chief can reel in a president when he’s headed toward the cliff — even a powerful, charismatic president like Ronald Reagan. One day in 1983, James A. Baker III, Mr. Reagan’s quintessential chief, got word that the president, enraged by a damaging leak, had ordered everyone who’d attended a national security meeting to undergo a lie-detector test. Mr. Baker barged into the Oval Office. “Mr. President,” he said, “this would be a terrible thing in my view for your administration. You can’t strap up to a polygraph the vice president of the United States. He was elected. He’s a constitutional officer.” Mr. Reagan’s secretary of state, George Shultz, who was dining with the president, chimed in, saying he’d take a polygraph but would then resign. Mr. Reagan rescinded the order that same day.Why did Mr. Meadows squander his career, his reputation and possibly his liberty by casting his lot with Mr. Trump? He once seemed an unlikely casualty of Mr. Trump’s wrecking ball — he was a savvy politician who knew his way around the corridors of power. In fairness to Mr. Meadows, three of his predecessors also failed as Mr. Trump’s chief. “Anyone who goes into the orbit of the former president is virtually doomed,” said Jack Watson, Jimmy Carter’s former chief of staff. “Because saying no to Trump is like spitting into a raging headwind. It was not just Mission Impossible; it was Mission Self-Destruction. I don’t know why he chose to do it.”In their motion to remove the Fulton County case to federal court, the lawyers for Mr. Meadows addressed Mr. Trump’s now infamous Jan. 2, 2021, call with Georgia’s secretary of state, Brad Raffensperger — during which Mr. Meadows rode shotgun as the president cut to the chase: “All I want to do is this. I just want to find 11,780 votes ….” Addressing Mr. Meadows’s role, his lawyers wrote: “One would expect a Chief of Staff to the President of the United States to do these sorts of things.”Actually, any competent White House chief of staff would have thrown his body in front of that call. Any chief worth his salt would have said: “Mr. President, we’re not going to do that. And if you insist, you’re going to make that call yourself. And when you’re through, you’ll find my resignation letter on your desk.”Mr. Meadows failed as Mr. Trump’s chief because he was unable to check the president’s worst impulses. But the bigger problem for our country is that his failure is a template for the inevitable disasters in a potential second Trump administration.Mr. Trump’s final days as president could be a preview. He ran the White House his way — right off the rails. He fired his defense secretary, Mark Esper, replacing him with his counterterrorism chief, Chris Miller, and tried but failed to install lackeys in other positions of power: an environmental lawyer, Jeffrey Clark, as attorney general and a partisan apparatchik, Kash Patel, as deputy C.I.A. director.Mr. Trump has already signaled that in a second term, his department heads and cabinet officers would be expected to blindly obey orders. His director of national intelligence would tell him only what he wants to hear, and his attorney general would prosecute Mr. Trump’s political foes.For Mr. Meadows, his place in history is secure as a primary enabler of a president who tried to overthrow democracy. But his example should serve as a warning of what will happen if Mr. Trump regains the White House. All guardrails will be gone.Chris Whipple is the author of “The Gatekeepers: How the White House Chiefs of Staff Define Every Presidency” and, most recently, “The Fight of His Life: Inside Joe Biden’s White House.”The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram. More