Prosecutors investigating Donald Trump's efforts to overturn the 2020 election in the US state of Georgia were expected to begin presenting evidence to a grand jury Monday for what could be a sprawling, multi-defendant indictment.

The case would be the fourth brought against Trump this year -- it could lead to the first televised trial of a former president, a watershed moment in US history, and feature charges typically used to bring down mobsters. 

Trump posted a number of messages to his Truth Social platform calling the matter "ridiculous" and urging a local election official whom he identified by name and called a "loser" not to testify to the grand jury.

"THOSE WHO RIGGED & STOLE THE ELECTION WERE THE ONES DOING THE TAMPERING, & THEY ARE THE SLIME THAT SHOULD BE PROSECUTED," Trump said, with his indictment expected before the end of Tuesday.

One incident highly likely to feature among the charges is a now infamous phone call Trump placed to Georgia officials asking them to "find" exactly the number of votes he would have needed to overturn his defeat to President Joe Biden.

Analysts are also expecting him to face charges over a scheme to send bogus certification of a supposed Trump victory in Georgia to the US Congress, as well as on false testimony given about election fraud by Trump aides.

The sweeping case could also bring in harassment of two Fulton County poll workers and the accessing of sensitive data from an elections office in a rural county south of Atlanta, one day after the 2021 Capitol riot.

A separate "special" grand jury heard from 75 witnesses last year and produced a secret report in February that, according to the foreperson, recommended numerous indictments.

Judicial analysts expect Atlanta-area prosecutor Fani Willis to wrap the allegations against Trump and several co-conspirators into one case under Georgia's Racketeer Influenced and Corrupt Organizations (RICO) law.

Racketeering statutes are usually used to target organized crime, but the broader Georgia law allows prosecutors to string together offenses committed by different people toward one common goal, criminal or not.

Georgia's court system is more transparent than the federal system, meaning there is no bar to the case being televised from the first preliminary hearing onwards. 

The grand jury in Fulton County meets on Mondays and Tuesdays, and local court-watchers expect Willis to conclude and bring any indictments that the panel approves within two days, her normal timeline for racketeering cases.

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