Once again, the US state of Georgia is the centre of a political firestorm.

On Tuesday, the justice department indicted Donald Trump over an alleged conspiracy to overturn the lawful results of the 2020 election in his favour.

The federal indictment devotes significant time to actions prosecutors say Mr Trump and his associates took in Georgia to challenge his loss.

An indictment in a state-level inquiry by Fulton County District Attorney Fani Willis could arrive in August. In a telling sign, officials recently erected barricades outside the county courthouse in Atlanta.

Mr Trump has denied any wrongdoing, attacking the investigations as politically motivated and a “witch hunt”. He has received fundraising bumps each time he is indicted, and has explicitly used the investigation to rally support from his base.

Opinion polling indicates that Mr Trump remains a clear frontrunner for the Republican presidential nomination.

While Mr Trump has already been charged in two other cases – over hush money payments in New York City, and over hoarding classified government files in Florida – it is the election cases in Georgia and Washington DC that may prove the most consequential.

“The potential Georgia case, and the federal case, go to the heart of our constitutional democracy,” said Emory Law School’s Morgan Cloud, “and whether we can keep it.”

Here’s what you need to know about Georgia’s role in the election interference investigations against Mr Trump.

After votes were tallied during the November 2020 presidential election, it was clear Mr Trump had lost the state of Georgia, and therefore the US presidency.

According to federal prosecutors led by special counsel Jack Smith, Mr Trump and his allies launched efforts to undermine the vote in six other battleground states, but Georgia stands out in the indictment.

Mr Trump went all out to reverse the results there, even as state officials, aides, and campaign staff warned that his claims of widespread election fraud had no basis in fact, the court document says.

There are four key incidents that appear in the federal indictment against Mr Trump, and are under investigation by the Atlanta office of Ms Willis, a Democrat.

On 2 January 2021, Mr Trump called Georgia’s secretary of state, a Republican named Brad Raffensperger, and said he just needed to “find 11,780 votes”, the number he would have required to beat Mr Biden.

Audio of the call was published by major US news outlets, causing a national uproar. Mr Trump has denied he was pressuring the secretary of state to fraudulently find enough votes for him to win, and called it a “perfect phone call”.

Ms Willis began her state inquiry in February 2021, after news of Mr Trump’s call to Mr Raffensperger broke.

During this time, Mr Trump was also pressuring other top Republican officials in the state to help him overturn the election results, including the attorney general and the Governor, Brian Kemp. They refused.

Mr Trump’s associates – most notably, his lawyer Rudy Giuliani – also spread false claims of voter fraud, and other conspiracy theories in Georgia.

According to the federal indictment, this included a presentation Mr Giuliani gave to Georgia state lawmakers in which he made a number of baseless assertions: that thousands of dead people voted in the state; that Georgia poll workers meddled with votes; that lawmakers had the power to decertify the state’s legitimate electoral college results. Mr Trump also amplified these claims on social media.

The former president’s allies also allegedly co-ordinated a scheme to have fake members of the Electoral College – the system that technically elects a US president – cast their votes for Mr Trump in Georgia, rather than Mr Biden, who won the state and so received its Electoral College votes. This scheme failed.

Both special counsel Jack Smith and Fani Willis, the Georgia prosecutor, have focused on the fake elector scheme in their investigations.

Finally, Trump campaign lawyers reportedly worked with a data firm to copy sensitive data from election systems in Coffee County, Georgia. The incident was part of a multi-state attempt by Mr Trump’s lawyers to access voting equipment, according to a Washington Post investigation. Ms Willis is said to be focusing on this incident.

We already know the justice department has indicted Mr Trump on four federal charges: conspiracy to defraud the US government; conspiracy to disrupt an official proceeding; obstructing an official proceeding; and deprivation of rights.

These charges relate to Mr Trump’s actions in Washington DC and nationwide, as well as in Georgia.

Legal experts say the former president could face a litany of legal troubles in Georgia.

In Georgia, Mr Trump may face fraud and conspiracy-related charges, including voter fraud and election fraud, as well as a potential count of obstruction of justice, depending on how Mr Trump responded to law enforcement inquiries into his conduct, said former federal prosecutor Neama Rahmani.

The call that Mr Trump made to Mr Raffensperger after the election will probably be the “crown jewel” of any forthcoming indictment, said Patrick Cotter, a former federal prosecutor.

“That will be the centrepiece, and that’s a significant, significant piece, not enough alone to convict anybody of anything, but if it’s filled out and augmented by other pieces of evidence, it could be very powerful,” he said.

Prosecutors will be looking to prove Mr Trump “crossed the line to fraud” and that his intent was to overturn Georgia’s election results during that call, said Mr Rahmani.

Mr Giuliani has also revealed he is a target of the Fulton County investigation.

Ms Willis might also bring a racketeering charge, which would make her case in Georgia distinct form the federal investigation.

The potential for that charge was bolstered by the allegations laid out in the federal indictment, said Mr Cloud of Emory Law School.

“Racketeering is defined as committing certain acts that are outlawed either under state law or federal law or both. Doing not just one crime, but a series of connected interrelated activities,” Mr Cloud explained.

“They can be interrelated based on common methods, common victims, or, most importantly here I’d say, a common purpose.”

In this case, “the specific common purpose would be, I think, to overturn the results in the state of Georgia”, Mr Cloud said.

The federal indictment showed the multiple interconnected activities that Mr Trump and his associates undertook in Georgia to undermine the election results, which we outlined above.

The cases against Mr Trump could proceed at both the state and federal level simultaneously, said Mr Cloud.

Mr Trump’s lawyers, meanwhile, will probably argue the former president never explicitly asked Georgia officials to tamper with the votes. The former president has denied all wrongdoing.

He has hired experienced lawyers in Georgia that have filed a number of motions to block various aspects of the investigation, including attempts to remove Ms Willis or change jurisdictions.

“I think they’re going to be very creative and very aggressive,” Mr Cloud said.