As Donald Trump became the first former president to face federal charges, he and his supporters went through a familiar routine of mounting a victimhood defense in the face of unprecedented allegations of wrongdoing. But this time, the stakes are higher.

Trump upped the level of his claims and threats as he faces the potential of years in prison if convicted on 37 charges of obstruction, illegal retention of defense information and other violations. Hours after pleading not guilty, Trump claimed he is being targeted by the special prosecutor, who is nonpartisan, for political reasons and vowed to retaliate against President Joe Biden if he is elected president in 2024.

"There was an unwritten rule" to not prosecute former presidents and political rivals, Trump told supporters in a speech at his golf club in New Jersey. "I will appoint a real special prosecutor to go after the most corrupt president in the history of America, Joe Biden, and go after the Biden crime family."

The vow is reminiscent of the "lock her up" chants against Democrat Hillary Clinton that Trump led during his 2016 campaign, but the new level of specificity alarmed many experts.

"If he did that, it'd be an authoritarian system, the end of a system of laws rather than of one man," said Lindsay Chervinsky, a presidential historian.

Even as he pledges to retaliate if elected, Trump and his supporters claim he is being targeted in a way that is similar to authoritarian regimes — such as in Russia, where opponents of President Vladimir Putin have been jailed, or Venezuela, where President Nicolas Maduro's chief rival was prosecuted. There is no evidence that Biden made the sort of pledge to target Trump that the former president has now made, and the president said he has never tried to influence the Justice Department on any case.

Trump's attacks on the justice system are the latest step in a now eight-year campaign by the former president and his allies against the traditions and institutions that have helped maintain American democracy.

Trump has long complained about being unfairly treated by the legal system, from contending that the judge in a lawsuit against his for-profit university was biased against him to targeting the FBI over its probe of Russian interference in his 2016 win. He even vowed retribution in that case, assigning a special prosecutor to review how the investigation into his campaign's possible coordination with Russia was handled, which led to only one conviction.

That track record makes his pledge of retribution more menacing, said Fred Wertheimer, president of Democracy 21, a group advocating for better government.

"He has shown repeatedly during his presidency that he is perfectly willing to misuse and abuse his office to carry out purely personal activities," Wertheimer said.

Stephen Saltzburg, a former top official in the criminal division of the Justice Department who is now a George Washington University law professor, said Trump was signaling that he would use the department to settle scores — just the thing he is claiming led to his indictment.

"This is typical of what Donald Trump does," Saltzburg said. "He essentially accuses people of doing what he would do if he were in the position."

The indictment came from a grand jury in Trump's adopted state of Florida after an investigation led by a special counsel, Jack Smith, who is independent of political appointees in the Biden administration and has previously prosecuted Democrats as well as Republicans. Speaking after the indictment was made public, Smith stressed that investigations such as the one into the documents follow the facts and the law.

"We have one set of laws in this country, and they apply to everyone," he said.

Many experts, of all political persuasions, said the charges against Trump stem from the proper functioning of the legal system, rather than a political vendetta. William Barr, Trump' s former attorney general, said the allegations in the indictment were serious and that Trump had no right to keep such documents.

"There is not an attorney general of either party who would not have brought today's charges against the former president," Michael Luttig, a former federal judge who was a conservative favorite for a Supreme Court post, wrote on Twitter.

According to the indictment, Trump held onto classified documents after leaving the White House, admitted on tape that they were classified and that he no longer had the presidential power to declassify them, then refused to return the records when the government demanded them back.

The former president's complaints about being persecuted, if not his vow of retribution, have been taken up by a wide swath of Republicans, from longtime supporters in Congress to governors who position themselves as moderates. That includes Virginia Gov. Glenn Youngkin, who bemoaned on Twitter what he called "a two-tiered justice system where some are selectively prosecuted, and others are not."

Another sign of how the right has absorbed Trump's world view came Tuesday night, hours after his court appearance, when Fox News briefly captioned images of Biden and Trump with the words "wannabe dictator speaks at the White House after having his political rival arrested." The network took down the chyron and said in a statement the matter was "addressed" without providing further details.

Trump's complaints about being persecuted are standard for former political leaders in other countries who are charged with crimes, said Victor Menaldo, a political scientist at the University of Washington.

"It makes sense politically if the leader has a rabid support group like Trump," Menaldo said. But in other countries, he said, the leaders are usually successfully prosecuted, and democracy continues.

The federal charges against Trump come two months after the Manhattan District Attorney's office charged him with 34 counts of falsifying business information in arranging payments to a porn star who said she had an affair with him. He also faces legal jeopardy in Fulton County, Georgia, where local prosecutors have launched a wide-ranging investigation of his attempt to have the state's electors assigned to him even though he lost the state to Biden in 2020, a result that was affirmed multiple times. A federal grand jury in Washington, D.C., continues to probe Trump's efforts to overturn his 2020 loss.

The Manhattan charges have drawn skepticism even from some Trump critics, who contend they're legally dubious. Trump's defenders — who include much of his own political party — don't make that distinction, condemning all probes of the former president. Indeed, after taking control of the House of Representatives following November's elections, Republicans empaneled a committee investigating the so-called "weaponization of government" against conservatives that is highlighting perceived injustices in the Trump probes.

The combination of the new federal charges, filed Friday, and the Republican presidential primary has led to stepped up complaints about scrutiny of the former president.

"I, and every American who believes in the rule of law, stand with President Trump against this grave injustice," House Speaker Kevin McCarthy tweeted after Trump announced the indictment against him. "House Republicans will hold this brazen weaponization of power accountable."

He and other Trump allies note that Biden also improperly had classified documents from his time as vice president — though there are big differences with the Trump case. The current president returned the records when requested and there is no evidence that he tried to conceal more, as is alleged with Trump. A second special prosecutor is looking at Biden's document handling.

Former U.S. Attorney Roscoe Howard said he has faith that the public will see past those protestations in the current case just by looking at the indictment.

"You can read it and make a determination of whether he's violating the law. And anybody who does the same thing, we treat them the same way," Howard said. "When you peel back some of the arguments we're hearing, it is a bit like, 'Oh I don't have to follow these rules.'"

That's the point when it comes to Trump, said Ruth Ben-Ghiat, a historian at New York University who studies authoritarians.

"It's an old situation he's in, but now because this is extremely serious, of course he's going to ramp up that narrative," Ben-Ghiat said. "What strongmen do is, if you are corrupt, you need to get back into power to shut down all the institutions that can harm you."