Federal indictments won’t stop Trump from running for president.

The second indictment against former President Donald J. Trump — this time for hoarding sensitive government documents — adds to the unusual questions raised by the spectacle of someone running for president while being indicted.

The indictment — and any conviction — would not stop Mr. Trump from running.

Nevertheless, it would be extraordinary for someone indicted, let alone convicted of a crime, to be a major party candidate.

There are only a few historical examples of somewhat serious candidates that even come close. They include the failed run in the 2016 Republican primary by former Texas governor Rick Perry after he was indicted on charges of abuse of power (the charges were dropped months after he dropped out of the race), and the 1920 run by Eugene V. Debs as a candidate for the Socialist Party while in prison for an espionage law conviction.

If Mr. Trump were elected president while a felony case was pending against him or after a conviction, many complications would ensue.

The Justice Department has historically taken the position that even suing a president while in office would be unconstitutional because it would impede the president from carrying out his duties as head of the executive branch. Mr. Trump would certainly try to get the case dismissed on that basis. There is no final ruling from the Supreme Court, because the issue has not been discussed before.

Most notably, in 1997, the Supreme Court allowed a federal lawsuit against President Bill Clinton while he was in office. However, that was a civil matter, not a criminal one. Mr. Trump also faces a state case, an indictment in Manhattan in April, where he is charged with falsifying business records in connection with a hush money payment.

Even more extraordinary complications would arise if Mr. Trump were convicted and imprisoned and elected anyway. One possibility is that he could win a federal court order requiring his release from prison due to a constitutional challenge. Another is that at the start of his second term, he could be immediately removed from office under the 25th Amendment for being “unable to exercise the powers and duties of his office”.