In Donald Trump’s world, judges have no business interfering with his business—or his politics. U.S. District Judge Gonzalo Curiel, Trump said, could not fairly judge the then-candidate’s eponymous university because Curiel is of Mexican descent and Trump wanted to build a wall with Mexico. The famously liberal 9th Circuit Court of Appeals should be broken apart, he said. A court challenge to Trump’s travel ban on immigrants from seven Muslim-majority countries? Not reviewable, Trump’s Justice Department lawyers argued. Trump labeled U.S. District Judge James L. Robart merely a “so-called judge” because he wrote an opinion blocking the travel ban. Even on a criminal matter—typically one where the judicial branch has the last word—the president delivered his unique trump card: he pardoned former Arizona sheriff Joe Arpaio, who was convicted of willfully violating a court order banning Arpaio from de facto immigration raids.

Judges are used to being the targets of criticism, and not just by the people they sentence to jail. Presidents in the past have made their frustration with the judicial branch known, whether it’s been by openly criticizing their decisions or attempting (as Franklin Roosevelt unsuccessfully did) to dilute any Supreme Court justice’s individual power.

But the new president has taken the battle to a new level, legal experts say, turning what has historically been a mostly-respectful turf war into an outright assault on the very integrity of the judicial branch, its officers, and even the rule of law.

“It’s always happened, because it’s politically expedient. It’s easy to attack a branch that can’t really protect itself,” since judges’ rulings are supposed to stand for themselves and jurists are not supposed to engage in back-and-forth political arguments with people about cases, says former U.S. District Court Judge Kevin Sharp, now managing partner of Sanford Heisler Sharp’s Nashville office. But the current attacks on the judicial branch, he says, are undermining not only the authority of judges to interpret the law but the public’s faith in those rulings.

“When you attack individual [judges], when you call them names, when you’re attacking their legitimacy, when you challenge someone’s ability to be fit and impartial because of their national origin—it challenges the legitimacy of the judiciary” as a whole, Sharp says.

“When the president is attacking one of the branches of government, it undermines the whole system of checks and balances. He is diminishing and degrading one of those branches,” says Notre Dame Law professor Jimmy Gurulé, a former federal prosecutor and assistant attorney general in the George H.W. Bush administration. “People are listening; people are paying attention” to Trump’s comments, “and they are going to be using this to their advantage,” Gurulé adds. If the chief executive does not respect the rulings of the judicial branch, “they will say, why should we comply? Why should we respect the decisions of the judiciary? I think it’s dangerous,” the former Bush administration official adds. “When you start eroding these fundamental institutions, there’s a risk of the erosion of democracy and respect for both democracy and the rule of law. It sets a very bad precedent.”

Other elected officials have criticized or sought to politicize the judiary as well. Texas Republican Senator Ted Cruz is among those who have suggested breaking up the 9th Circuit Court of Appeals, arguing that California’s judges are dominating more conservative jurists from the western states circuit. North Carolina’s GOP legislature recently required that candidates for judgeships list their party affiliations on the ballot. The North Carolina General Assembly reduced the size of the state Court of Appeals, depriving the new Democratic governor, Roy Cooper, from naming replacements for GOP picks.

Legal scholars and historians note that Trump is hardly the first president to criticize judicial decisions or express his frustration with the judicial branch. Presidents and Legislative Branch Members, after all, have to face elections and are accountable to the public on a regular basis, while federal judges are appointed for life. That frees jurists from some political pressure, ideally making them more devoted to the rule of law than their own job security. But it can be agitating to elected officials who watch their policy agendas limited or undone by judges whose decisions are generally the last word.

FDR famously proposed expanding the Supreme Court to as many as 15 justices, a 1937 idea that grew out of his frustration that the high court had declared elements of his New Deal unconstitutional. The so-called “court-packing plan” (it would have added an additional associate justice when sitting justices 70 and older refused to retire) was defeated overwhelmingly in the Senate. Roosevelt was able to make appointments to fill vacancies during his presidency and ironically, by 1942, all but two members of the high court were his appointees.

Harry S. Truman tangled with the high court as well, notes William and Mary Law School professor Neal E. Devins, director of the school’s Institute of Bill of Rights Law. Truman had inherited some of FDR’s court and was incensed that the justices struck down as unconstitutional Truman’s effort to seize the U.S. steel industry as a wartime emergency move (though the Korean War had not actually been declared a war). Truman took it personally, later saying, “I don’t see how a court made up of so-called ‘Liberals’ could do what that court did to me.”

Brown v. Board of Education, the 1954 Supreme Court ruling striking down segregated schools, also had a political ripple effect, notes University of San Francisco Law School dean John Trasviña, leading to the 1956 Southern Manifesto of regional lawmakers declaring Brown v. Board of Education as an abuse of judicial power that squelched states’ rights. President Barack Obama, meanwhile, openly criticized the Supreme Court’s Citizens United ruling that struck down key elements of the Bipartisan Campaign Reform Act of 2002. And he did so in the most public of ways, making his remarks at a State of the Union address attended by six members of the high court. All of the justices remained expressionless during Obama’s criticism except Justice Samuel Alito, who could be viewed mouthing the words “not true.”

Meanwhile, the court appointments themselves have become more political and partisan—at least in the eyes of voters and elected officials, who openly discuss having “liberal” or “conservative” allies on the bench. That impression is amplified by attention to high-profile, closely-decided cases such as the ruling making same-sex marriage the law of the land, experts say.

Most cases are decided unanimously or near-unanimously by the high court, Devins says, but “elected officials are seeing the court in more partisan terms than they ever have before.”

Trump, meanwhile, has escalated the conflict from a sort of rock-paper-scissors game, where each branch of government triumphs at different times, to an all-out war on the very integrity of the judicial branch, critics say. The undermining has been as brazen as Trump’s public statements and tweets—as was the case with his attack on Curiel—and as subtle as a legal argument to the federal court of appeals. In February, during 2017 arguments before the 9th Circuit Court of Appeals, for example, the Justice Department claimed that the court did not have the right to review the executive order. That was startling to legal experts, who say that the administration could have argued, with precedent, that the courts are supposed to give deference to the executive on matters involving national security.

“Even with that [traditional] deference, the administration’s position was, judges shouldn’t decide it,” says Trasviña, who is also former counsel to the Senate Judiciary Committee. “It wasn’t even a matter of saying, ‘Give us great deference.’ It was, ‘Don’t even look at us.’”

Trump’s pardon of Arpaio, too, might not have the cable news appeal of brandishing insults at judges, experts say, and on its face, was a limited-impact executive decision. But because Arpaio had been convicted of defying a court ruling, Trump’s official forgiveness was a way of saying that judges don’t really count and that the president can do (or undo) their work, say critics.

“The pardon is not legally significant,” in that people generally agree that Trump had the constitutional power to pardon the former sheriff, says Arizona attorney James Goodnow, a partner at the law firm Fennemore Craig. “But it was symbolic, in how Joe Arpaio thumbed his nose at the rule of law. Using his pardon power on Joe Arpaio was really encouraging and supporting that kind of conduct. We live in a world of checks and balances,” Goodnow adds. “Donald Trump doesn’t like checks. And he certainly doesn’t like balances.”

Jurists should expect to be aggressively questioned and criticized—if for no other reason than that they are protected by lifetime terms, say Washington, D.C., attorney Ilan Wurman, who served as general counsel on Republican Rand Paul’s presidential campaign. And while jurists may see their rulings as academic—even arcane—matters of law, elected officials, and voters are feeling the real-life impact “in some respects. Judges bear at least some responsibility for the political attacks that are brought upon them, because judging is seen as political today, whereas historically, even if it was political, it wasn’t considered political,” Wurman says.

So while the high court might have upheld Obamacare or same-sex marriage on the justices’ majority interpretation of the Constitution, “rightly or wrongly, half of the country thinks they have been robbed of a fair fight,” Wurman says.

The attacks on the judiciary come as public support for the country’s institutions is waning—an average of 32 percent overall, a 2016 Gallup poll found, with the Supreme Court clocking in at 36 percent. The problem, Gurulé says, is that not only will judicial decisions have less power if elected officials or the pubic see no need to adhere to them, but that the U.S.’ influence over other nations is in peril.

Democracy “is supposed to be based on [the U.S.] model, Gurulé says. “So it is a big deal. He needs to be called out on this as it being serious and dangerous to the rule of law and to democracy. It’s really setting a bad precedent for other countries that are working and sacrificing and trying to set up a democracy.”

But given political tensions in the U.S.—and the political dividends elected officials receive by blaming a branch of government that is, by definition, supposed to be above politics—such aggressive challenges are likely to continue, experts say. “Attacking the independence of the judiciary is nothing new. We have a long, if not proud, tradition of this in the United States,” says Kansas University School of Law professor Lumen N. Mulligan, author of four books on legal jurisdiction and procedure. “In part, it is the job of the judiciary to take it and stand firm. All that said, attacking the judiciary comes at a cost,” he adds.