Trump Wants to Prosecute Biden. He Also Thinks Presidents Deserve Immunity.

When a lawyer for former President Donald J. Trump argued before the Supreme Court last week that his client should be immune from charges of plotting to subvert the last election, he asked the justices to picture a world in which former presidents were ceaselessly pursued in the courts by their successors.

“Could President Biden someday be charged with unlawfully inducing immigrants to enter the country illegally for his border policies?” the lawyer, D. John Sauer, asked.

What Mr. Sauer did not mention was that Mr. Trump has done as much as anyone to escalate the prospect of threatening political rivals with prosecution. In 2016, his supporters greeted mentions of Hillary Clinton with chants of “lock her up.” In his current campaign, Mr. Trump has explicitly warned of his intent to use the legal system as a weapon of political retribution, with frequent declarations that he could go after President Biden and his family.

In effect, Mr. Trump has asked the Supreme Court to enforce a norm — that in the United States, public officials do not engage in tit-for-tat political prosecutions — that he has for years threatened to shatter. In promising to sic his Justice Department on Mr. Biden, Mr. Trump has laid the grounds for the very conditions that he was asking the justices to guard against by granting him immunity.

Mr. Trump’s perspective is that it is Mr. Biden who has politicized justice by pursuing him on multiple fronts as they face each other on the campaign trail. In making that argument, however, Mr. Trump has sought to evade the reality that no former president has been faced with as many allegations, or as much evidence, of wrongdoing as he has.

The two federal cases against Mr. Trump were brought by a special counsel operating largely independently of the Justice Department, while the two other criminal cases against him were brought by local district attorneys in New York and Georgia.