Atlanta, Georgia - A second Donald Trump campaign lawyer reached a plea deal on Friday that would see him testify for the prosecution in the case alleging that the former US president led a criminal conspiracy to overturn his 2020 election loss in Georgia.

Kenneth Chesebro (62) was indicted on racketeering and other charges in August along with the former president and 17 other co-defendants.

Chesebro was accused of orchestrating a plan to submit a slate of fake electors to Congress in a bid to block certification of Democrat Joe Biden's election victory over Trump.

Jury selection for his trial began on Friday at the Fulton County Courthouse in Atlanta, Georgia, but was abruptly halted after Chesebro entered into a surprise last-minute plea deal with prosecutors.

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Chesebro, a graduate of Harvard Law School, faced seven charges including racketeering – a felony that carries jail time – conspiracy to commit forgery, and conspiracy to file false documents.

He pleaded guilty to the single charge of conspiracy to file false documents in exchange for a sentence of five years probation, $5,000 in restitution, and 100 hours of community service.

"You are to testify truthfully in any other proceedings in this case against any and all other co-defendants," Superior Court Judge Scott McAfee added at the plea hearing.

Chesebro is the third co-defendant in the Georgia case to enter a guilty plea.

Chesebro's guilty plea came one day another former Trump campaign attorney, Sidney Powell, also entered into a plea deal with prosecutors that would see her testify at the upcoming trials of the other co-defendants.

Powell (68) was a vocal Trump supporter who pushed outlandish conspiracy theories about foreign manipulation of voting machines. She pleaded guilty to six misdemeanor counts of conspiracy to interfere with the performance of election duties and was sentenced to six years of probation.

Legal analysts said the plea deals are a potential blow to Trump, who is accused of leading a criminal conspiracy to overturn the 2020 election result in Georgia, where Biden won by some 12,000 votes.

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In addition to having two of his former lawyers testifying against him, Trump and his attorneys will also no longer be able to have an early look at the evidence and strategy that prosecutors may have used at his own eventual trial.

Chesebro and Powell had been the only two of the 19 co-defendants in the racketeering case to invoke their right to a speedy trial.

An Atlanta trial date has not been set yet for Trump, the frontrunner for the 2024 Republican presidential nomination, and the other co-defendants.

Trump also faces federal charges for his efforts to upend the 2020 election in relation to the January 6, 2021 storming of the US Capitol by his supporters. He is to go on trial in that case in Washington in March 2024.