Former President Donald J. Trump now faces a very different legal challenge in the culmination of a more than two-year Atlanta investigation into election interference.ATLANTA — The indictment of Donald J. Trump in New York over hush-money payments to a porn star was a global spectacle, with the former president glumly returning to his old stomping grounds in Manhattan as TV networks closely tracked his procession of black SUVs on their way to the courthouse.But strip away the high drama, and the actual charging document in the case was far less grand — 34 felony counts of a fairly narrow and common bookkeeping charge that Alvin L. Bragg, the Manhattan district attorney, described as the “bread and butter” of his office’s white-collar criminal prosecutions.In Georgia, however, there is another criminal investigation of Mr. Trump nearing completion, this one also led by a local prosecutor, Fani T. Willis of Fulton County. While nothing is certain, there are numerous signs that she may go big, with a more kaleidoscopic indictment charging not only Mr. Trump, but perhaps a dozen or more of his allies.Her investigation has targeted a wide range of conduct centered around efforts to subvert the democratic process and overturn Mr. Trump’s 2020 election loss. Nearly 20 people are already known to have been told that they are targets who could face charges, including Rudolph W. Giuliani, Mr. Trump’s former personal lawyer, and David Shafer, the head of the Georgia Republican Party.For Mr. Trump, the possibility of a second and potentially more complex criminal indictment in another state underscores the blizzard of legal challenges he is facing, even as he emerges as the clear front-runner among Republican presidential candidates.For Ms. Willis, the choice to pursue a narrowly focused indictment or more a sprawling one — a classic prosecutor’s dilemma — carries with it potential risks and benefits on both sides. And American history offers few examples in which the stakes are so high.Fani T. Willis, the district attorney for Fulton County, Ga., has said that seeking an indictment under the state’s Racketeer Influenced and Corrupt Organizations, or RICO, statute is an option that she is considering.Audra Melton for The New York Times“Certainly prosecutors would have this conversation of what’s in the best interest of justice and what is strategically preferable for a case,” said Barbara McQuade, a law professor at the University of Michigan and former federal prosecutor. A narrow case can be easier for jurors to understand. But it is also possible to go “too narrow,” Ms. McQuade said, denying a jury the ability to see the entire scope of a defendant’s criminal behavior.If, on the other hand, a wide-ranging scheme is charged, “you allow them to see the full scope of criminal conduct,” she said. But going big could cause jurors to become lost amid a profusion of evidence, with a long trial increasing the possibility of a mistrial.In Georgia, the investigation is focused on myriad efforts to overturn Mr. Trump’s narrow loss in Georgia after his 2020 election defeat, including his January 2021 phone call to Brad Raffensperger, the Georgia secretary of state, in which he pressed Mr. Raffensperger, a fellow Republican, to recalculate the results and “find” him enough votes to win.Mr. Trump is also under investigation by Jack Smith, a special counsel appointed by Attorney General Merrick B. Garland, for his role in the events leading up to the Jan. 6, 2021, attack on the Capitol and his decisions to retain sensitive government documents at his home in Florida.If Ms. Willis chooses to seek indictments in the Georgia case, she may do so after a new grand jury begins its work in the second week of May, though nothing is set in stone. Typically, presenting such cases to a regular grand jury is a short process that takes a day or two.The wide scope of the investigation has been evident for months, and Ms. Willis has said that seeking an indictment under the state’s Racketeer Influenced and Corrupt Organizations, or RICO, statute is an option that she is considering. Like the similar federal law, the Georgia RICO statute allows prosecutors to bundle what may seem to be unrelated crimes committed by a host of different people if those crimes are perceived to be in support of a common objective.Election workers counted absentee ballots in Atlanta in 2020.Audra Melton for The New York TimesMs. Willis has extensive experience with racketeering cases, including a case she won involving a group of public-school educators accused of altering students’ standardized tests. Her office is currently pursuing racketeering charges against two gangs connected to the hip-hop world, including one led by the Atlanta rapper Jeffery Williams, who performs as Young Thug.“I think jurors are very, very intelligent,” Ms. Willis said at a news conference in August, in which she announced a racketeering case against a third Atlanta-area gang known as Drug Rich. “RICO is a tool that allows a prosecutor’s office or law enforcement to tell the whole story. And so we use it as a tool so that they can have all the information they need to make a wise decision.”After starting the Trump investigation in February 2021, Ms. Willis’s office sought the aid of a special grand jury to gather and consider evidence. In Georgia, such juries do not have indictment powers but can issue subpoenas in long-running investigations. The body was empaneled last spring and completed its work in January after hearing closed-door testimony from 75 witnesses, though its recommendations have remained largely under seal.Emily Kohrs, the forewoman of that special grand jury, strongly hinted in an interview with The New York Times in February that Mr. Trump was among more than a dozen people who had been recommended for indictment. “You’re not going to be shocked,” she said, when asked whether Mr. Trump was named in the report. “It’s not rocket science.”Court records show that the special grand jury sought testimony from witnesses including Mark Meadows, who served as White House chief of staff under Mr. Trump; Senator Lindsey Graham of South Carolina, an ally of the former president; and Trevian Kutti, a former self-described publicist for rapper Kanye West who, according to prosecutors, was involved in a plot to force a Fulton County elections worker to give a false confession of election fraud.Documents also show that prosecutors are following numerous narrative threads in Georgia involving either Mr. Trump or his allies. These include Mr. Trump’s phone calls to Georgia officials, including the one to Mr. Raffensperger; specious statements about election fraud made by Mr. Giuliani and others at state legislative hearings; the convening of pro-Trump electors to the Electoral College at the Georgia State Capitol; Ms. Kutti’s bizarre meeting with the elections worker, Ruby Freeman, two days after Mr. Trump’s phone call to Mr. Raffensperger, in which Mr. Trump falsely accused Ms. Freeman of being a “vote scammer”; and a plot by allies of Mr. Trump involving the copying of sensitive election software in rural Coffee County, Ga.In Georgia, the investigation is focused on efforts to overturn Mr. Trump’s loss in Georgia after his 2020 election defeat, including his January 2021 phone call to Brad Raffensperger, the Georgia secretary of state, in which he pressed Mr. Raffensperger to “find” him enough votes to win.Audra Melton for The New York TimesThe battle lines have already been drawn. Mr. Trump has steadfastly maintained his innocence and used inflammatory language to assail the prosecutors in both Georgia and New York. And last month, his legal team in Georgia filed a 52-page motion, with more than 400 additional pages of exhibits, challenging a case that has yet to be filed. Legal experts saw it as a sign of what’s to come.“That’s indicative of the type of motions you’ll see if there’s an indictment,” said Melissa D. Redmon, a law professor at the University of Georgia who has been a prosecutor in Fulton and Clayton Counties. “Every single step is going to be challenged from the beginning.”In New York, Mr. Bragg said he, too, was focusing on crimes that thwarted the democratic process, though these were from the 2016 campaign. In a statement, he said that Mr. Trump had “repeatedly and fraudulently falsified New York business records to conceal crimes that hid damaging information from the voting public during the 2016 presidential election.” He is accused of covering up a potential sex scandal involving the porn star Stormy Daniels.Mr. Trump more than once has compared his legal tribulations to those of the notorious Chicago mob boss Al Capone. He said on social media, as recently as February, that he had more lawyers working for him than Capone, who was famously found guilty in 1931 and sentenced to 11 years in prison for tax evasion — hardly the most lurid or troubling of his many misdeeds.Mr. Bragg’s decision in New York opened him up to intense criticism from Republicans, who have called the charges flimsy and politically motivated, and the alleged offenses insufficient to merit the nation’s first indictment of a former president. Even some Democrats note that the New York charges seem pedestrian compared with the allegations looming against Mr. Trump elsewhere.“Is it as problematic as Jan. 6 or what happened at Mar-a-Lago? No,” David Pepper, the former chairman of the Ohio Democratic Party, said recently, referring to federal investigations into Mr. Trump’s efforts to overturn the 2020 election and his handling of classified documents. “But that doesn’t mean you don’t investigate it.”If Ms. Willis brings a sprawling RICO case, it could present its own problems, said Michael J. Moore, a former U.S. attorney for the Middle District of Georgia. Asking a jury to consider multiple acts that do not tie directly back to Mr. Trump might make it more difficult “to point the finger at him with the strength that you might have been able to in a simpler case,” he said.Mr. Moore also wondered how far a trial involving Mr. Trump would stretch into the coming presidential election season. He noted that the jury selection process in the multi-defendant racketeering case involving Young Thug had been going on for roughly four months, and that the judge in the case had estimated the trial could take up to nine months.“We’re just going to have to face the reality that we’re going to have to deal with that,” he said. More