Kenneth Chesebro on Friday became the second lawyer in two days to plead guilty in a criminal racketeering indictment that also named Donald J. Trump.
Mr. Chesebro also agreed to cooperate with state prosecutors in Fulton County, Ga., who have accused him, Mr. Trump and 17 others of conspiring to overturn the 2020 election. On Thursday, Sidney K. Powell made a similar deal and said she, too, would cooperate with the prosecutors.
Mr. Chesebro was accused of conspiring to create slates of fake electors to support Mr. Trump in Georgia and several other states won by President Biden. His lawyers had argued that he was merely offering legal counsel to clients.
Prosecutors contend that attempts to seat the pro-Trump electors were part of an illegal scheme to keep Mr. Trump in power, and Mr. Chesebro’s cooperation is considered valuable in the effort to prove their case.
Mr. Chesebro, 62, pleaded guilty to a single felony charge of conspiracy and was sentenced to five years’ probation. He was originally charged with seven felonies, including one charge under the state racketeering law.
Both Mr. Chesebro and Ms. Powell had exercised their right to a speedy trial under Georgia law, and had been preparing for jury selection to start on Monday.
With a trial date for Mr. Trump and the other remaining co-defendants unclear for now, the formerly fast-moving Georgia case is now on pause. At the same time, Mr. Chesebro’s plea has added to a sense of momentum in favor of the Georgia prosecutors, although it was unclear on Friday whether other defendants were considering plea deals.
As part of his deal, Mr. Chesebro agreed to “truthfully testify” against the remaining co-defendants, as had Ms. Powell and Scott Hall, an Atlanta bail bondsman who was the first to accept a plea deal in the case in late September. Mr. Chesebro also agreed to turn over documents and other evidence relevant to the case.
The two consecutive plea deals spell only bad news for Mr. Trump and his 15 remaining co-defendants, including Rudolph W. Giuliani, his former personal lawyer, and Mark Meadows, his former White House chief of staff.
Emails obtained by The New York Times show that Mr. Chesebro was considering not only the legality of various maneuvers related to the electors scheme in the weeks after the election, but also their political ramifications, potentially undercutting arguments that he was merely offering legal advice. One email chain included messages from John Eastman, another conservative lawyer who has been charged in the Georgia case.
On Friday, Mr. Chesebro appeared in a dark suit at the defense table at around noon — soon after several hundred potential jurors gathered on the seventh floor of the courthouse to fill out screening questionnaires ahead of his imminent trial. Judge Scott McAfee of Fulton County Superior Court told the prospective jurors that the trial was expected to last four or five months, and acknowledged that it was likely that they would be familiar with a case that had made international headlines.
Prosecutors acknowledged in court last month that a deal would be offered to Mr. Chesebro, and ABC News reported this week that he rejected a deal in which he would plead guilty to a felony racketeering charge, a conviction that could have resulted in him losing his law license. But he pleaded guilty to a charge that does not automatically strip him of his license, and Mr. Chesebro’s lawyer said he expects him to keep it.
Mr. Chesebro is the first person with inside knowledge of the wide-ranging plan to create fake slates of pro-Trump electors in states that Mr. Trump actually lost to have pleaded guilty and agreed to cooperate with the authorities.
He was identified, albeit not by name, as Co-Conspirator 5 in a federal election interference indictment that the special counsel, Jack Smith, filed against Mr. Trump in Washington this summer. In that indictment, Mr. Chesebro is described as a lawyer who helped to craft and implement “a plan to submit fraudulent slates of presidential electors to obstruct the certification process.”
The Washington indictment cited several emails in which Mr. Chesebro and other lawyers working on the fake elector scheme had expressed reservations about whether it was honest or even legal.
It remains unclear how Mr. Chesebro’s cooperation deal with prosecutors in Georgia might affect Mr. Smith’s prosecution of Mr. Trump. If Mr. Chesebro takes the stand in Fulton County, Mr. Smith’s prosecutors could in theory use his testimony against him should they ultimately decide to bring charges.
Scott R. Grubman, a lawyer for Mr. Chesebro and a former federal prosecutor, said on Wednesday that a Justice Department policy discourages bringing federal charges against someone who pleads guilty to a crime in a separate case “unless there are very, very specific circumstances.”
“When you’re convicted or plead guilty, what’s supposed to happen is that that’s it,” he said. ”And so I really hope Jack Smith will, seriously, take those obligations seriously. “
The fact that there will be no trial next week for Mr. Chesebro and Ms. Powell, who pleaded guilty to six misdemeanor counts, is a strategic boon for prosecutors. Because they were going to have to lay out large sections of their case against all the defendants to prove that the two at trial were part of a sweeping racketeering conspiracy, lawyers for Mr. Trump and others would have been effectively offered a preview of the case that they would have to defend against.
In a statement on Friday, Steven H. Sadow, Mr. Trump’s lead lawyer in Georgia, said that Mr. Chesebro’s guilty plea appeared to be influenced by “the looming threat of prison time.”
“However,” he added, “it is very important for everyone to note that the RICO charge and every other count was dismissed. Once again, I fully expect that truthful testimony would be favorable to my defense strategy.”
As part of his plea, Mr. Chesebro was also instructed to write a letter of apology to the state of Georgia (he said he had already done so) and to pay $5,000 in restitution to the Georgia secretary of state’s office.
Christian Boone contributed reporting from Atlanta.