In the two and a half years since a mob laid siege to the Capitol in an effort to prevent Congress from certifying Joseph R. Biden Jr.’s electoral victory, a wealth of evidence has emerged about Donald J. Trump’s bid to stay in power after the 2020 election.

Mr. Trump and his allies peddled spurious claims of voter fraud, pressured officials in states he narrowly lost and recruited false slates of electors in those states. He urged Vice President Mike Pence to delay certification of Mr. Biden’s win. And he called on a huge crowd of his supporters to march on the Capitol and “fight like hell.”

Now, Mr. Trump appears almost certain to face criminal charges for some of his efforts to remain in office. On Tuesday, he disclosed on social media that federal prosecutors had sent him a so-called target letter, suggesting that he could soon be indicted in the investigation into the events that culminated in the riot.

Mr. Trump did not say what criminal charges, if any, the special counsel, Jack Smith, had specified in issuing the letter.

But since the Capitol attack — in part because of revelations by a House committee investigation and news reports — many legal specialists and commentators have converged on several charges that are particularly likely, especially obstruction of an official proceeding and conspiracy to defraud the government.

A person briefed on the matter said the target letter cited three statutes that could be applied in a prosecution of Mr. Trump by the special counsel, Jack Smith, including a potential charge of conspiracy to defraud the United States.

Norman Eisen, who worked for the House Judiciary Committee during Mr. Trump’s first impeachment and contributed to a prosecution memo modeling potential Jan. 6-related charges, said that the target letter suggested the special counsel “has more than enough evidence” to bring a case against the former president.

“By leading the effort to procure fraudulent electoral certificates across the nation, Trump helmed a conspiracy to defraud the U.S.,” Mr. Eisen said. “And by using those false documents to press Mike Pence to disrupt the Jan. 6 meeting of Congress, Trump attempted to obstruct an official proceeding.”

There have also been signs that prosecutors have explored potential charges involving wire or mail fraud related to Mr. Trump’s fund-raising efforts in the name of overturning the election results.

Any charges in the District of Columbia — where federal grand juries have been hearing evidence — would raise additional legal peril for Mr. Trump. Already, the Justice Department has won guilty pleas or convictions in hundreds of cases related to the riot, suggesting that a pool of jurors may be less receptive toward him than in Palm Beach County, Fla., where he faces charges over his hoarding of sensitive government documents at his Mar-a-Lago estate.

These are some of the charges Mr. Trump could face in the Jan. 6 case.

Corruptly Obstructing an Official Proceeding

Both the House committee that scrutinized Jan. 6 and a federal judge in California who intervened in its inquiry have said that there is evidence that Mr. Trump tried to corruptly obstruct Congress’s session to certify Mr. Biden’s Electoral College victory. Under Section 1512(c) of Title 18 of the United States Code, such a crime would be punishable by up to 20 years in prison.

Prosecutors have already used that law to charge hundreds of ordinary defendants in Jan. 6 cases, and in April, a federal appeals court upheld the viability of applying that charge to the Capitol attack. Still, unlike ordinary rioters, Mr. Trump did not physically participate in the storming of the Capitol.

In issuing criminal referrals as it ended its investigation, the Jan. 6 committee argued that Mr. Trump should be charged under the statute based on two sets of actions. By summoning supporters to Washington and stoking them to march on the Capitol, lawmakers argued, Mr. Trump had violated that law. Mr. Trump’s lawyers would likely raise doubts over whether he intended for his supporters to riot in part because he also told them to protest “peacefully.”

The committee also cited Mr. Trump’s participation in the fake electors scheme as a reason to issue charges, pointing to his effort to strong-arm Mr. Pence to cite the existence of slates of electors pledged to Mr. Trump in seven states that Mr. Biden had actually won as a basis to delay certifying the election. The panel stressed how Mr. Trump had been told that there was no truth to his claims of a stolen election, which it said showed his intentions were corrupt.

Conspiring to Defraud the Government and to Make False Statements

Both the federal judge in California and the Jan. 6 committee also said there was evidence that Mr. Trump violated Section 371 of Title 18, which makes it a crime, punishable by up to five years in prison, to conspire with another person to defraud the government.

The basis for such a charge would be similar: Mr. Trump’s interactions with various lawyers and aides in his effort to block the certification of Mr. Biden’s electoral victory, even though Mr. Trump was repeatedly told that his allegations of widespread voter fraud were baseless.

In his ruling last year in a civil lawsuit over whether the Jan. 6 committee could obtain the emails of John Eastman, a legal adviser to Mr. Trump in his fight to overturn the election results, Judge David O. Carter ruled that it was more likely than not that the communications involved crimes, so qualified for an exception to attorney-client privilege.

“The illegality of the plan was obvious,” he wrote. “Our nation was founded on the peaceful transition of power, epitomized by George Washington laying down his sword to make way for democratic elections. Ignoring this history, President Trump vigorously campaigned for the vice president to single-handedly determine the results of the 2020 election.”

A conspiracy to submit false electors to Congress could also implicate Section 1001, which makes false statements a crime punishable by up to five years in prison. In the documents case, Mr. Trump is charged under this statute, accused of having caused his lawyer to lie to the Justice Department.

Wire and Mail Fraud

A constellation of other potential crimes has also surrounded the Jan. 6 investigation. One is wire fraud. Section 1343 of Title 18 makes it a crime, punishable by 20 years in prison, to cause money to be transferred by wire across state lines as part of a scheme to obtain money by means of false or fraudulent representations. A similar fraud statute, Section 1341, covers schemes that use the Postal Service.

Subpoenas issued by Mr. Smith suggest that he has been scrutinizing Mr. Trump’s political action committee, Save America PAC. It raised as much as $250 million, telling donors the money was needed to fight election fraud even as Mr. Trump had been told repeatedly that there was no evidence to back up those claims.

The House Jan. 6 committee had also suggested that Mr. Trump and his associates had defrauded his own supporters. It described how after the election, they appealed to donors as many as 25 times a day to help fight the results in court and contribute to a defense fund. But no such fund existed, and they used the money for other purposes, including spending more than $200,000 at Trump hotel properties.

“Throughout the committee’s investigation, we found evidence that the Trump campaign and its surrogates misled donors as to where their funds would go and what they would be used for,” Representative Zoe Lofgren, Democrat of California, said during one hearing. “So not only was there the big lie. There was the big rip-off.”

The Jan. 6 committee and some legal commentators have also suggested Mr. Trump could be charged under Section 2383 of Title 18, which makes it a crime to incite, assist, “aid or comfort” an insurrection against the authority and laws of the federal government. That offense, however, is rarely charged and has not been leveled against any Jan. 6 defendant to date.

In its final report, the committee singled out five of Mr. Trump’s other allies — Mark Meadows, his final chief of staff; and the lawyers Rudolph W. Giuliani, Mr. Eastman, Jeffrey Clark and Kenneth Chesebro — as potential co-conspirators with Mr. Trump in actions the committee said warranted Justice Department investigation.

Luke Broadwater contributed reporting.