Trump’s Next Legal Threat Could Be in Georgia. That May Be Tricky for Federal Prosecutors.

WASHINGTON — The Fulton County district attorney’s investigation into former President Donald J. Trump’s effort to overturn the 2020 election in Georgia is nearing a decision point, posing fresh challenges for federal prosecutors considering charging him in connection with the Jan. 6, 2021, attack on the Capitol.

The long-running investigation by Fani T. Willis in Atlanta substantially overlaps with the broader inquiry into Mr. Trump’s conduct by the special counsel, Jack Smith, in Washington. Both rely on similar documentary evidence, some of the same criminal targets and a small, shared pool of witnesses with knowledge of the former president’s actions and intent.

Mr. Trump’s critics believe the concurrent investigations provide assurance that the former president and architects of the scheme to install fake electors in battleground states, including Rudolph W. Giuliani and John C. Eastman, will be held to account.

But they also create complications for two aggressive investigative teams pursuing some of the same witnesses, increasing the possibility of discrepancies in testimony that Mr. Trump’s lawyers could exploit. Ms. Willis and her team have a head start, having begun their work in February 2021, and are expected to seek indictments early next month. That raises the pressure on Mr. Smith, who has pledged to work quickly, to move even faster, according to current and former prosecutors.

“Normally, the lead federal prosecutor just picks up the phone and tries to work it out with the local prosecutor, but it’s obviously a lot more difficult in a case of this magnitude,” said Channing D. Phillips, who served as acting United States attorney for the District of Columbia from March to November 2021. “The stakes of not working things out are incredibly high.”

The investigative efforts are by no means the same. Mr. Smith’s purview extends into other areas, most notably the investigation into whether Mr. Trump mishandled classified documents that were found at his Mar-a-Lago estate after he left office.

The federal investigation into Jan. 6 focuses on several charges, according to two law enforcement officials: wire fraud for emails sent between those pushing the false electors scheme; mail fraud for sending the names of electors to the National Archives and Records Administration; and conspiracy, which covers the coordination effort. (A fourth possible charge, obstruction of an official proceeding before Congress, has been used in many cases brought against participants in the Capitol attack.)

And some of Ms. Willis’s work has been more parochial in nature, including a review of false statements that Trump allies like Mr. Giuliani made at state legislative hearings in December 2020.

Justice Department officials said the indictment of Mr. Trump by the Manhattan district attorney, Alvin L. Bragg, over a hush money payment to a porn star will have little effect on their investigations. Federal prosecutors in Manhattan passed on bringing a similar case.

But the Georgia investigation is entirely different. The Justice Department has no authority to order local prosecutors to step aside in areas where the investigations do overlap, unless their investigations conflict with federal law. In fact, internal department rules discourage indicting the subjects of prior state prosecutions.

Moreover, there is “no formal rule book” for settling jurisdictional questions or for deciding the chronological sequence of prosecutions, and disputes are usually hashed out informally, as they arise, on an ad hoc basis, said Preet Bharara, a former U.S. attorney for the Southern District of New York.

Local and federal prosecutors routinely work together to coordinate charging decisions based on which jurisdiction offers better chances of conviction or a stiffer sentence. But in many high-profile cases, prosecutors view dueling investigations as a nuisance or even a hazard.

Witnesses, even forthright ones, sometimes offer different accounts when interviewed by lawyers representing different offices. Differences between state and federal laws can lead to damaging conflicts over strategy and priorities. Then there is what is known as “witness fatigue,” when important players simply grow tired or uncooperative after running gantlets of government inquisitors.

Fulton County prosecutors are conducting a wide-ranging investigation that includes calls made by Mr. Trump to exert pressure on state officials and efforts by the former president and his allies to replace legitimate electors in Georgia with pro-Trump alternates. Last year, Ms. Willis’s office sought to interview two key figures who had served in the Justice Department: Richard Donoghue, the acting deputy attorney general in the waning days of the Trump administration, and Jeffrey Clark, an assistant attorney general who led the department’s environmental division.

Shortly after Mr. Trump left office, it emerged that Mr. Clark had tried to circumvent the department’s leaders and aid Mr. Trump’s efforts to stay in power. He even drafted a letter that was to have been sent to lawmakers in Georgia falsely claiming that the Justice Department had “identified significant concerns” that would affect the state’s election results and urging lawmakers to convene a special session.

Mr. Donoghue was alarmed when he saw the draft, according to testimony he provided to the House committee that investigated the Jan. 6 attack.

Aides to Ms. Willis filed what are known as Touhy requests, named after a 1951 Supreme Court case. Under the rule, local prosecutors are required to get authorization from the Justice Department to question its current or former employees. But the requests were ultimately rejected.

It is not clear why the department rejected the requests. But both men were at the center of an investigation into Mr. Clark’s conduct by the Justice Department’s inspector general that was subsequently handed off to Mr. Smith’s team.

A spokesman for Mr. Smith declined to comment.

Fulton County prosecutors also declined to comment. The forewoman of an Atlanta special grand jury that issued an advisory report in January, which has remained largely under seal, appeared to hint in an interview this year that it had recommended that Mr. Trump be indicted.

The Atlanta case has put additional pressure on Mr. Smith. Justice Department officials have said they wanted to make charging decisions in the spring or summer, before the 2024 election kicks into high gear — which raises the question of whether Mr. Smith will try to bring charges before Ms. Willis does.

“Looking at this as a federal prosecutor, I would just want to go first,” said Joyce Vance, a University of Alabama law professor who served as the U.S. attorney in Birmingham from 2009 to 2017. “I don’t want to have to try my case after it’s already been brought in a state court. You really want to go first to avoid problems with witnesses, and other technical or legal problems.”

If Ms. Willis moves first, Mr. Smith’s team would have to obtain department approval to waive an internal rule that precludes “multiple prosecutions and punishments for substantially the same act(s).”

That is not considered a high bar, however. Mr. Smith would simply have to show that the state case did not completely cover all the issues addressed in a federal case. It is believed that exemption was recently used to obtain a hate crimes conviction against three men who murdered Ahmaud Arbery, a young Black man who was jogging through their neighborhood.

John P. Fishwick Jr., a former U.S. attorney for the Western District of Virginia, said he often requested that local prosecutors step aside when he thought their investigations conflicted with his. He suggested that Mr. Smith could at least consider asking Ms. Willis to do the same.

“D.O.J. and state prosecutors do not play well in the same sandbox, but at the end of the day, if it gets into a tug of war, D.O.J. is usually going to win,” he said. “The federal government just has more power as far as compelling witnesses, more power to assign people to a case and more oomph, in general.”

While prosecutors should clear up disputes over access to witnesses and documents, it is vital that the two efforts be seen as independent and fact-driven and not a “witch hunt,” as Mr. Trump has described all of the investigations into him, former Justice Department officials say.

“I don’t think they would coordinate on things like timing or language of the charges or anything like that — although that wouldn’t be illegal,” said Mary McCord, a former top official in the department’s national security division who is now a visiting professor at Georgetown University Law Center.

“But the goal here is avoid any appearance that they are coordinating prosecutions for political purposes,” added Ms. McCord.

Glenn Thrush and Adam Goldman reported from Washington, and Danny Hakim from New York.