WASHINGTON - The House Jan. 6 committee’s final report asserts Donald Trump criminally engaged in a “multi-part conspiracy” to overturn the lawful results of the 2020 presidential election and failed to act to stop his supporters from attacking the U.S. Capitol, concluding an extraordinary 18-month investigation into the former president and the violent insurrection two years ago. Mr. Trump “lit that fire,” the committee’s chairman, Mississippi Congressman Bennie Thompson, writes.

The 814-page report released Dec. 22 comes after the panel interviewed more than 1,000 witnesses, held 10 hearings and obtained more than a million pages of documents. The witnesses — ranging from many of Mr. Trump’s closest aides to law enforcement to some of the rioters themselves — detailed Mr. Trump’s “premeditated” actions in the weeks ahead of the attack, and how his wide-ranging efforts to overturn his defeat directly influenced those who brutally pushed past the police and smashed through the windows and doors of the Capitol on Jan. 6, 2021.

The insurrection gravely threatened democracy and “put the lives of American lawmakers at risk,” the bipartisan nine-member panel concluded, offering a definitive account of a dark chapter in modern American history. It functions not only as a compendium of the most dramatic moments of testimony from months of hearings, but also as a document that is to be preserved as a warning for future generations.

In a series of recommendations, the seven Democrats and two Republicans on the committee suggest that Congress consider barring Mr. Trump from holding future office. The findings should be a “clarion call to all Americans: to vigilantly guard our Democracy and to give our vote only to those dutiful in their defense of our Constitution,” says House Speaker Nancy Pelosi in a foreword to the report.

The report’s eight chapters tell the story largely as the panel’s hearings did this summer — describing the many facets of the remarkable plan that Mr. Trump and his advisers devised to try and void President Biden’s victory. The lawmakers detail the former president’s pres- sure on states, federal officials, lawmakers and Vice President Mike Pence to game the system or break the law.

In the two months between the election and the insurrection, the report says, “President Trump or his inner circle engaged in at least 200 apparent acts of public or private outreach, pressure, or condemnation, targeting either State legislators or State or local election administrators, to overturn State election results.”

Mr. Trump’s repeated, false claims of widespread voter fraud resonated with his supporters, the committee said, and were amplified on social media, building on the distrust of government he had fostered for his four years in office. And he did little to stop them when they resorted to violence and stormed the Capitol, interrupting the certification of President Biden’s victory.

The massive, damning report comes as Mr. Trump is running again for the presidency and also facing multiple federal investigations, including probes of his role in the insurrection and the presence of classified documents at his Florida estate. This week is particularly fraught for him, as a House committee voted to release his tax returns after he has fought for years to keep them private. At the same time, Mr. Trump has been blamed by Republicans for a worse-than-expected showing in the recent midterm elections, leaving him in his most politically vulnerable state since he was elected in 2016.

Looking forward, the committee makes several suggestions for action, including an overhaul of the Electoral Count Act, the election law that Mr. Trump tried to circumvent. Bipartisan legislation to make it harder for lawmakers to object to presidential results, and for the vice president to intervene, is set to be passed as part of year-end spending legislation on Friday and sent to President Biden for his signature.

The panel also notes in that section that the 14th Amendment to the U.S. Constitution holds that anyone who has taken an oath to uphold the Constitution can be prevented from holding office for engaging in insurrection or rebellion.

Mr. Trump “is unfit for any office,” writes the committee’s vice chairwoman, Republican Rep. Liz Cheney of Wyoming.

Posting on his social media site, Mr. Trump called the report “highly partisan” and falsely claimed it didn’t include his statement on Jan. 6 that his supporters should protest “peacefully and patriotically.” The committee did include that statement, noting that he followed it with election falsehoods and charged language exhorting the crowd to “fight like hell.”