The evidence collected by the Jan. 6 committee and in some of the federal cases against those involved in the Capitol attack poses for Attorney General Merrick Garland one of the most important questions any attorney general has ever faced: States United Should Indict Former President Donald Trump?

The basic allegations against Mr. Trump are well known. In defiance of the advice of many of his closest aides, including Attorney General William Barr, he falsely claimed that the 2020 presidential election was fraudulent and stolen; he lobbied Vice President Mike Pence to refuse to count certified electoral votes for Joe Biden in the Jan. 6 congressional tally; and he raised a crowd, led it to the Capitol, and for a time refused to take any action to stop the violence that ensued.

To indict Mr. Trump for these and other acts, Mr. Garland must make three decisions, each more difficult than the last, and none of which has an obvious answer.

First, he must determine whether the decision to indict Mr. Trump is his. If Mr. Garland decides a criminal investigation of Mr. Trump is warranted, Justice Department regulations require him to appoint a special counsel if the investigation presents a conflict of interest for the department and if Mr. Garland believe that such an appointment would be in the public interest.

The department undoubtedly faces a conflict of interest. Mr. Trump is a political opponent of Mr. Garland’s boss, President Biden. Mr. Trump is also Mr. Biden’s most likely political opponent in the 2024 presidential election. Mr. Garland’s judgments impact Mr. Biden’s political fate and eventual term in office. The appearance of a conflict escalated when Mr. Biden allegedly told those around him that Mr. Trump was a threat to democracy and should be prosecuted, and complained about Mr. Garland’s lingering on the question.

Even in the event of a conflict, Mr. Garland could retain full control of Mr. Trump’s legal fate if he believes a special counsel would not serve the public interest. Some would argue that the public interest in an impartial prosecution would be best served by the appointment of a quasi-independent special counsel, perhaps a member of Mr. Trump’s party.

But no matter who conducts it, a criminal investigation into Mr. Trump would take place in a polarized political environment and an overheated media environment. In this context, Mr. Garland could legitimately conclude that the public interest demands that the Trump case be guided by the politically responsible person whom the Senate confirmed in 2021 by a vote of 70-30.

If Mr. Garland opens a Trump investigation and proceeds with the case — decisions he may have already made — the second question is whether he has enough evidence to indict Mr. Trump. The fundamental question here is whether, under the terms of the Justice Department guidelines, Mr. Trump’s actions constitute a federal offense and “admissible evidence will likely be sufficient to obtain and sustain a conviction.”

These will be difficult conclusions for Mr. Garland to draw. He should believe that the department could probably convince a unanimous jury that Mr. Trump committed crimes beyond a reasonable doubt. Mr. Garland cannot base this judgment on the factual accounts or unilateral legal assertions of the January 6 committee. Nor can he place much weight on a ruling by a federal judge who, in a dispute over a civil subpoena — a process that requires a significantly lower standard of proof to prevail than in a criminal trial — ruled. concluded that Mr. Trump (who was not pictured) “more likely than not” committed a crime related to Jan. 6.

Instead, Mr. Garland must assess how any charges against Mr. Trump would fare in an adversarial criminal proceeding administered by an independent judge, where Mr. Trump’s lawyers will challenge the government’s factual and legal assertions, give his version of the events, will raise many defenses. and appeal any material adverse court rulings to the Supreme Court.

The two most frequently mentioned crimes that Mr. Trump may have committed are corrupt obstruction of official process (the January 6 vote count) and conspiracy to defraud the United States (by attempting to cancel the election results). Many have noted that Mr. Trump can plausibly defend these charges by arguing that he had no criminal intent because he truly believed massive voter fraud had taken place.

Mr. Trump would also claim that key elements of his allegedly criminal actions — his interpretations of the law, his pressure on Mr. Pence, his delay in responding to the Capitol breach and more — were exercises of his constitutional prerogatives as as general manager. Mr. Garland is expected to assess how these legally powerful claims illuminate the applicability of criminal laws to Mr. Trump’s actions in what would be a president’s first criminal trial. He would also consider the negative implications of a Trump lawsuit for more virtuous future presidents.

If Mr. Garland concludes that Mr. Trump has committed punishable crimes, he would face the third and most difficult decision: whether the national interest would be served by prosecuting Mr. Trump. This is not a question that legal analysis alone can resolve. It is a judgment on the nature and fate of our democracy.

Failure to indict Mr. Trump under these circumstances would imply that a president — who cannot be charged while in office — is literally above the law, in defiance of the very notion of constitutional government. It would encourage anarchy in future presidents, any more than Mr. Trump would if he won the next election. In contrast, the rule of law would be vindicated by a condemnation of Trump. And that could be bolstered by a full judicial broadcast of Mr. Trump’s possible crimes in office, even if that ultimately fails.

And yet, Mr. Garland cannot be sure that a Trump lawsuit would promote national reconciliation or bolster confidence in American justice. Indicting a past and future political adversary of the current president would be a cataclysmic event from which the nation would not soon recover. This would be seen by many as politicized retribution. The lawsuit would take many years to conclude; would last and have a profound impact on the next elections; and would leave the ultimate fate of Mr. Trump to the next administration, which may be led by Mr. Trump.

Along the way, the accusation would further inflame our already flamboyant partisan acrimony; consume the remainder of Mr. Biden’s term; embolden, and possibly politically empower, Mr. Trump; and threaten to spark tit-for-tat recriminations in presidential administrations. The prosecution could thus jeopardize Mr. Garland’s cherished goal of restoring the Justice Department’s standards of “independence and integrity” even if he prosecutes Mr. Trump in service of those standards. And if the prosecution fails, many will conclude that the country and the rule of law have suffered tremendously for nothing.

Mr. Garland’s decisions will be deeply controversial and will have consequences beyond his life. It’s easy to see, unlike his many critics, why he gathers as much information as possible — including what emerged from the Jan. 6 committee and the prosecution of senior officials involved in the Capitol breach — before making these memorable judgments.

Jack Goldsmith, a Harvard law professor and senior fellow at the Hoover Institution, is co-author of “After Trump: Reconstructing the President.”