WASHINGTON — Declaring that the central cause of the Jan. 6, 2021, attack on the Capitol was “one man,” the House committee investigating the assault delivered its final report on Thursday, describing in extensive detail how former President Donald J. Trump had carried out what it called “a multipart plan to overturn the 2020 presidential election” and offering recommendations for steps to assure nothing like it could happen again.

It revealed new evidence about Trump’s conduct, and recommended that Congress consider whether to bar Trump and his allies from holding office in the future under the 14th Amendment’s ban on insurrectionists.

“The central cause of Jan. 6 was one man, former President Donald Trump, whom many others followed,” the report said. “None of the events of Jan. 6 would have happened without him.”

The release of the full report was the culmination of the panel’s 18-month inquiry and came three days after the committee voted to formally accuse Trump of inciting insurrection, conspiracy to defraud the United States, obstruction of an act of Congress and one other federal crime as it referred him to the Justice Department for potential prosecution. While the referrals do not compel federal prosecutors to take any action, they sent a powerful signal that a select committee of Congress believes the former president committed crimes.

“Our institutions are only strong when those who hold office are faithful to our Constitution,” Rep. Liz Cheney, R-Wyoming, and the vice chairwoman of the committee, wrote in the report. “Part of the tragedy of Jan. 6 is the conduct of those who knew that what happened was profoundly wrong, but nevertheless tried to downplay it, minimize it or defend those responsible.”

The report contains the committee’s recommendations, which are intended to prevent future presidents from attempting a similar plot. The panel has already endorsed overhauling the Electoral Count Act, the law that Trump and his allies tried to exploit on Jan. 6 in an attempt to cling to power.

Among committee recommendations were a possible overhaul of the Insurrection Act and strengthening the enforcement of the 14th Amendment’s ban on insurrectionists holding office.

The panel also said Congress should consider bolstering its subpoena power and increasing penalties against those who threaten election workers. And it said bar associations should consider whether any of the lawyers who aided Trump should be punished.

The report went into great detail about a supporting cast of lieutenants who enabled him. Mark Meadows, his final chief of staff, and lawyers John Eastman, Rudy Giuliani, Jeffrey Clark and Kenneth Chesebro were named as potential “co-conspirators” in Trump’s various attempts to cling to power.

Trump bashed the report on his social media site, Truth Social, calling it “highly partisan.”

The report was largely an expanded version of the panel’s widely watched set of hearings this summer — which routinely drew more than 10 million viewers — with its chapter topics mirroring the themes of those sessions.

The chapters include Trump’s spreading of lies about the election, the creation of fake slates of pro-Trump electors in states won by President Biden, and the former president’s pressure campaign against state officials, the Justice Department and former Vice President Mike Pence. It documents how Trump summoned a mob of his supporters to Washington and then did nothing to stop them as they attacked the Capitol for more than three hours.

It documented how, at times, even Trump did not believe or take seriously some of the outlandish claims about election fraud being promoted by him and his allies. During a conference call two weeks after Election Day, lawyer Sidney Powell asserted that “communist money” had flowed through countries like Venezuela, Cuba and perhaps China to interfere with the election.

According to testimony provided to the committee by Hope Hicks, a former top aide to Trump, he “muted his speakerphone and laughed at Powell, telling the others in the room, ‘This does sound crazy, doesn’t it?’”

At the same time, it showed how Trump encouraged his most extreme supporters to back him as he energized protesters massing in Washington on Jan. 6, with an organizer of his rally that day noting that he “likes the crazies.”

The nine-member panel was made up of seven Democrats and two Republicans, all of whom gained new prominence through the tightly scripted and highly produced televised hearings.

“Our country has come too far to allow a defeated president to turn himself into a successful tyrant by upending our democratic institutions, fomenting violence and, as I saw it, opening the door to those in our country whose hatred and bigotry threaten equality and justice for all Americans,” Rep. Bennie Thompson, D-Mississippi, and the committee’s chairman, wrote in a foreword to the report.

Among those who received significant criticism in the report was Giuliani, Trump’s personal lawyer, whom he assigned to find ways to stop Biden from assuming power and Trump from losing it.

The committee’s report traced Giuliani’s post-election behavior from the moment Trump put him in charge of legal strategy shortly after the election to his efforts to directly pressure officials in battleground states.

“Rudy was just chasing ghosts,” the report quotes Trump’s former deputy campaign manager, Justin Clark, as saying of the earliest days after the election.

“The Big Lie,” the first chapter, recounts how Trump engaged in a premeditated plan starting on election night to falsely claim that he had won and claim that outstanding votes were fraudulent — and that he went on making those claims for months even after being informed repeatedly by his aides that he was wrong and had lost.

“Donald Trump was no passive consumer of these lies,” the report said. “He actively propagated them. Time and again President Trump was informed that his election fraud claims were not true. He chose to spread them anyway.”

Chapter 2, titled “I Just Want to Find 11,780 Votes,” recounts how Trump sought to pressure officials in Georgia to find the votes he needed to swing the state, which had been won by Biden. It goes on to explore Trump’s largely unsuccessful pressure campaign on a wide array of officials in other swing states he had lost to find ways to reverse the outcome.

Subsequent chapters cover the genesis of the so-called fake electors scheme, in which Trump and his allies sought to promote alternative slates of electors from states he had lost to try to block or delay certification of Biden’s victory, and Trump’s campaign to pressure Pence to bring the fake elector plan to fruition.

Trump was largely reliant on Eastman to provide legal justification for Pence in effect unilaterally deciding whether to accept the outcome of the election, but the report shows that he turned to other aides to help make the case as well. It says that either Trump or Meadows gave John McEntee, director of the Presidential Personnel Office, the job of researching the matter further.

Though McEntee was one of Trump’s close advisers, he was not a lawyer and had no relevant experience.

As Pence resisted and Trump castigated him publicly, officials became increasingly concerned about the vice president’s safety. On the morning of Jan. 6, the report says, “an agent in the Secret Service’s intelligence division was alerted to online chatter “regarding the V.P. being a dead man walking if he doesn’t do the right thing.’”

Chapter 6, called “Be There, Will Be Wild!,” recounts how Trump “summoned a mob for help” through a Twitter post on Dec. 19 that promoted a pro-Trump protest scheduled for Jan. 6 in Washington — a message, the report said, that “focused his supporters’ anger on the joint session of Congress” that would take place that day.

Far-right groups like the Oath Keepers and the Proud Boys mobilized, as did adherents of the QAnon conspiracy theory, the report said.

The report goes on to describe Trump’s three hours of inaction as violence swept across Capitol Hill and some of his supporters called for Pence to be hanged.

Another chapter analyzes the attack on the Capitol itself, showing how the Proud Boys and Oath Keepers appeared to storm the building in a deliberate fashion, and how many individual protesters came to Washington with firearms. Eleven minutes after protesters breached the Capitol building, Trump tweeted angrily about Pence. The violence would continue for hours.

The committee later asked McEntee about Trump’s demeanor during a phone call between the two of them at the end of the day after the violence had been quelled — and specifically about whether Trump expressed sadness.

“No,” McEntee said, according to the report. “I mean, I think he was shocked by, you know, it getting a little out of control, but I don’t remember sadness, specifically.”

One appendix in the report detailed the flood of threats about the potential for violence that law enforcement officials received before Jan. 6, and concluded that the failure to share and act on those threats “jeopardized the lives of the police officers defending the Capitol and everyone in it.”

More than 150 officers were injured during the day’s bloody assault.

For instance, on Dec. 26, 2020, the Secret Service received a tip about the Proud Boys having “a large enough group to march into D.C. armed and will outnumber the police so they can’t be stopped.”

It stressed, “Their plan is to literally kill people,” adding: “Please, please take this tip seriously and investigate further.”