ATLANTA — President Trump and 18 allies, including Mayor Giuliani, were indicted in Georgia on Monday, accused of scheming in a “criminal enterprise” to overturn his 2020 election loss in the state. It’s the fourth criminal case to be brought against the 45th president and the second this month to allege that he tried to subvert the results of the vote.

In remarks late Monday, the Fulton County district attorney, Fani Willis, noted the scale of the indictment, which spans 97 pages and features 41 charges of criminality, but also that the accused were entitled to the presumption of innocence.

Ms. Willis said she was setting a deadline for Mr. Trump and his co-defendants to “surrender” by noon on Friday, August 25, and said that she sought to begin the trial within six months, but that the judge in the case would decide the schedule. She indicated that she anticipated trying all of the 19 accused plotters together.

The indictment details dozens of acts by Mr. Trump and his allies to undo his defeat in the battleground state, including hectoring Georgia’s Republican secretary of state to find enough votes to keep him power, pestering officials with unsubstantiated claims of voter fraud, as well as attempting to persuade Georgia lawmakers to ignore the election results and appoint a new slate of electoral college electors favorable to Trump.

Mr. Trump and his alleged co-conspirators are described in the indictment as having “constituted a criminal organization whose members and associates engaged in various related criminal activities,” using legal terms associated with Georgia’s Racketeer Influenced and Corrupt Organizations, or RICO, law.

The indictment relies on the RICO law to charge Mr. Trump and his associates for allegedly conspiring to overturn the state’s 2020 election result. Mr. Trump and his co-defendants, the indictment alleges, formed “an ongoing organization whose members and associates functioned as a continuing unit for a common purpose of achieving the objectives” of what prosecutors call a “criminal enterprise.”

“Trump and the other Defendants charged in this Indictment refused to accept that Trump lost, and they knowingly and willfully joined conspiracy to unlawfully change the outcome of the election in favor of Trump,” says the indictment issued Monday night by Ms. Willis’ office.

Mr. Trump’s campaign denounced Ms. Willis in comments late Monday as a “rabid partisan who is campaigning and fundraising on a platform of prosecuting President Trump through these bogus indictments.”

Other defendants included the former White House chief of staff, Mark Meadows; Mr. Giuliani and John Eastman, Mr. Trump’s personal attorneys; and a Trump administration Justice Department official, Jeffrey Clark, who advanced his efforts to undo his election loss in Georgia.

The indictment bookends a remarkable crush of criminal cases — four in five months, each in a different city — that would be daunting for anyone, never mind a defendant simultaneously running for president.

It comes just two weeks after the Justice Department special counsel charged him in a conspiracy to overturn the 2020 election results.

Though the Georgia indictment is centered on Mr. Trump’s efforts to subvert election results in just one state, its sprawling web of defendants stands apart from the more tightly-targeted case brought by special counsel Jack Smith, which so far only names Mr. Trump as a defendant.

The Georgia case also stands out because, unlike the two federal prosecutions he faces, Mr. Trump would not have the opportunity to try to pardon himself if elected president.

As indictments mount, Mr. Trump — the leading Republican candidate for president in 2024 — often invokes his distinction as the only former president to face criminal charges. He is campaigning and fundraising around these themes, portraying himself as the victim of Democratic prosecutors.

The indictment charges Trump with making false statements and writings for a series of claims he made to Georgia’s secretary of state, Brad Raffensperger, and other state election officials on January 2, 2021, including that up to 300,000 ballots “were dropped mysteriously into the rolls” in the 2020 election, that more than 4,500 people voted who weren’t on registration lists and that a Fulton County election worker, Ruby Freeman, was a “professional vote scammer.”

There are other charges related to allegedly trying to get a public official to violate an oath, conspiracy to impersonate a public officer, conspiracy to commit forgery, as well as conspiracy to commit false statements and file false documents.

Mr. Trump also stands accused of violating his oath of office.