Jan. 6 Rioters Have Been Held to Account. That Might Be the Easy Part.

When Enrique Tarrio, the former leader of the Proud Boys, was sentenced on Tuesday to 22 years in prison for his central role in planning the attack on the Capitol, it marked an inflection point in the Justice Department’s vast investigation of the events of Jan. 6, 2021.

The sentence ended a series of three federal trials centered on seditious conspiracy, the most serious offense to have emerged from more than two and a half years of investigation of the pro-Trump mob that took part in the attack. But it also punctuated a shift in public attention away from the people in boots who broke through barricades or shattered windows at the Capitol to those in suits who concocted plans to subvert the vote count or spread lies about election fraud that ultimately set the scene for violence.

The effort to hold the rioters at the Capitol accountable has been the largest inquiry ever undertaken by the Justice Department, and is likely to continue for months, or even years, with additional indictments.

But the looming trials of former President Donald J. Trump and those accused of helping him seek to remain in office will be a different sort of challenge, probing the resilience and authority of the criminal justice system.

The Trump prosecutions are likely to be a stress test of the country’s commitment to the rule of law at a moment of intense polarization and with Mr. Trump solidifying his position as the Republican Party’s presumptive presidential nominee.

As if more tension were needed, Mr. Trump has already shown that he intends to make attacking the integrity of the proceedings a central part of his campaign, saying on Wednesday that he plans to take the stand in his own defense.

In some sense, it turns out, prosecuting people — even more than 1,000 of them — for attacking the police or for disrupting the election certification has been relatively straightforward. That is largely because the assault on the Capitol was a discrete event that can be picked apart forensically and in many, if not most, of the riot cases clear-cut video footage exists of the defendants committing crimes.

More than half of the 1,150 people charged in the attack so far have already pleaded guilty. Of the dozens who have risked going to trial, only two — a former government contractor and a onetime Broadway singer affiliated with the Oath Keepers militia — have been fully acquitted.

But Mr. Trump’s trials — especially the two he faces on charges of election interference, which were brought in Washington by the special counsel, Jack Smith, and in Georgia by the Fulton County district attorney, Fani T. Willis — will be of a different nature. They will be wrapped up in a tangled web of legal and political complexities that has never been seen before.

Samuel Buell, a former federal prosecutor and a law professor at Duke University, said that Mr. Trump’s election cases were legally challenging not only because they involved intersecting plots with numerous co-conspirators, but also because they were likely to hinge on thorny issues like proving intent and determining liability for crimes that different people may have committed together.

As if to prove his point, prosecutors in the Georgia case said on Wednesday that they expect to call at least 150 witnesses and that the trial there could last four months. (The judge said it might take eight.)

“These cases are much more nuanced and complicated than the riot cases,” Mr. Buell said.

In the federal case in Washington alone, the former president’s lawyers have already promised to file an array of pretrial motions, including one that would involve an untested legal argument that Mr. Trump is immune to the charges because the indictment covers a period when he served as the nation’s commander in chief. Citing the unprecedented nature of the case, the lawyers have said they are also planning to portray the prosecution as a direct attack on Mr. Trump by his chief political rival, President Biden.

“This is one of the most unique cases from a legal perspective ever brought in the history of the United States,” John F. Lauro, who is representing Mr. Trump in the matter, said in court last week.

Complicating matters will be Mr. Trump himself, who has already been cautioned by the judge in his Washington case to avoid making statements out of court that could intimidate witnesses or taint the jury pool. But within days of the warning, Mr. Trump was already testing the boundaries of the judge’s order — and her patience — by posting messages on his social media website that largely amplified criticism others had lodged against her.

At least for the moment, both of Mr. Trump’s election trials are scheduled to open on March 4, the day before Super Tuesday, when 15 states are scheduled to hold Republican primaries or caucuses. Even if that timeline ultimately shifts, Mr. Trump — who is facing two more trials next year related to his handling of classified materials and to hush money payment to a porn actress — will most likely have to stop campaigning for long stretches of the spring and summer just as his attempts to secure the nomination will come to their crescendo.

If Mr. Trump’s obligations in the courthouse keep him from the campaign trail, he might decide to bring the campaign trail to the courthouse. Indeed, there could be two Donald Trumps on display when the trials finally start: one, under the watchful eye of judges, will have to follow a measure of decorum; the other, on social media or in the glare of TV cameras, may feel less inhibited.

Even though the Capitol riot cases and Mr. Trump’s election prosecutions both converge on the events of Jan. 6, the two for now are wholly separate.

Last week, Judge Amit P. Mehta, who has overseen several riot cases, including the sedition case of the Oath Keepers’ leader, Stewart Rhodes, reflected on that separation at a sentencing hearing for Sandra Parker, a member of the far-right group.

In a pensive moment on the bench, Judge Mehta noted how “the power of disinformation” and the rampant lies about the election had caused defendants like Ms. Parker “to believe in something that really was unbelievable.”

The pervasiveness of frauds like that, the judge said, was one of the “untold” stories of the Capitol attack, but that same story will be prominently featured in Mr. Trump’s election trials.

To be sure, none of the charges Mr. Trump is facing accuse him of encouraging or inspiring the violence at the Capitol. At worst, the Washington indictment claims that as chaos broke out at the building on Jan. 6, Mr. Trump “exploited the disruption” to further his goal of stopping the election certification.

The Justice Department spent considerable effort searching for links between the White House and the rioters and, at least so far, has never publicly established any direct ties between the boots and the suits. What remains to be seen is whether prosecutors find a way to bridge their inquiry into the Capitol attack to their investigation into Mr. Trump’s attempts to overturn his electoral defeat.

“We have the fraud charges and we have the seditious conspiracy charges,” said Daniel C. Richman, a former federal prosecutor and a law professor at Columbia University. “But what we don’t yet have is any link between the two beyond vague inferences and thoughts.”