Yet another likely criminal indictment is looming over Donald Trump this week, which would deepen his already extreme legal quagmire and further divert an unparalleled election season from the campaign trail into multiple courtrooms.

Atlanta-area prosecutor Fani Willis, a Democrat, has called at least two key witnesses to appear before a grand jury on Tuesday in a sign that her probe into the ex-president's bid to overturn his 2020 election loss in Georgia, a vital swing state, is nearing its end game. Willis is expected to seek charges against more than a dozen people. Trump believes he will be among them and is already fundraising off of the possibility of more criminal charges, casting them as Democratic efforts to interfere in the 2024 election.

If Trump does face any fresh charges, they would follow three previous indictments. He's already facing a March trial in Manhattan over business fraud charges related to a 2016 hush money payment to an adult film actress. He's also facing federal charges from special counsel Jack Smith's two probes -- in Florida, into his mishandling of classified documents, and in Washington, DC, over his efforts to subvert the 2020 election. He's pleaded not guilty in all the cases against him so far.

But there will be key differences between the potential case in Georgia and Trump's previous indictments. While Trump's 2024 campaign has predominantly become an extension of his legal defense, any possible trial and conviction in Georgia would be far harder for him to meddle with if he is elected to a second term since presidential powers that could help him interfere with federal cases do not extend to local matters.

"Not only would he not be able to pardon himself, but the pardon process in Georgia means Gov. (Brian) Kemp would not be able to pardon him either. There's a pardon board. So it's a more complicated process," former federal prosecutor Renato Mariotti said on "CNN Newsroom" on Saturday. "He also would not be able to shut down the investigation in the same way."

If he wins the White House in November 2024, Trump could potentially make an argument in state courts that he's immune from state indictments, but that would set off a complex period of constitutional litigation. He could, however, install an attorney general in Washington who could shut down Smith's federal investigations.

The potential charges in Georgia could be more profound than in the case brought by Manhattan District Attorney Alvin Bragg, which is also not a federal case. They would cover conduct from Trump's time as a sitting president and he's now the Republican front-runner to run in a general election in which Georgia is likely to be a key battleground.

There are also indications that a Willis case would be the broadest yet arising out of the post-election drama in 2020. She has been eyeing charges under the Racketeer Influenced and Corrupt Organizations Act (or RICO), which would allow her to sketch a comprehensive narrative of an alleged conspiracy involving multiple actors. While Smith referred to multiple co-conspirators in his indictment of Trump over post-election activity, he has not yet charged others -- possibly in an effort to get the case involving the former president before a jury quickly, given the political significance of an approaching election.

Expectations that the Willis investigation is reaching its critical point ahead of possible indictments grew when the state's former lieutenant governor -- Geoff Duncan, a Republican and now a CNN commentator -- said on Saturday he'd been told to appear before a Fulton County grand jury on Tuesday. Independent journalist George Chidi posted on social media that he had received a similar summons. CNN previously reported that Democratic state Sen. Jen Jordan had received subpoenas to testify before a grand jury later this month.

How Trump asked officials to 'find' votes

The Georgia case would likely be anchored to Trump's efforts to pressure Republican election officials in the Peach State to defy the will of voters and hand him victory in 2020, including in a call in which he asked Georgia's GOP Secretary of State Brad Raffensperger to "find" sufficient votes for him to overtake Biden's lead.

Trump has claimed the call with Raffensperger was "perfect."

But an exclusive report by CNN over the weekend hinted at the vast scope of the Willis investigation and the gravity of the potential charges. Prosecutors have text messages and emails directly connecting members of Trump's legal team to the breach of a voting system in Coffee County, Georgia, early in January 2021, sources said. Investigators have long suspected the breach was not an organic effort sprung from sympathetic Trump supporters in the Republican stronghold. They have gathered evidence indicating it was a top-down push by Trump's team to access sensitive voting software, according to people familiar with the situation.

None of the allegations against Trump or his team have yet been tested in court, and he has already denied all wrongdoing. But the investigation seems likely to point to yet another serious attempt to overturn American democracy to keep Trump in power.

A political and legal collision amid an unprecedented campaign

Any new charges against Trump will most immediately create an extraordinary situation with the first Republican primary debate scheduled for Milwaukee next week. Normally the first such clash would be a moment for candidates to create a strong early impression as they seek to leap out of the pack. But the event risks being completely overshadowed by Trump's tribulations as his GOP rivals delicately seek to profit from his growing liabilities. They must navigate making the argument that he's unelectable in a general election without alienating Republican base voters who regard the ex-president as a persecuted hero. Trump has not said whether he will show up to the debate.

New charges against Trump would also add to the collision of legal proceedings and trials expected next year at a time when he would normally be barnstorming the country with rallies -- especially if he converts his lead in most primary polling into his third straight presidential nomination.

Smith, for example, has asked a judge to open a trial into the election interference charges in January -- just two weeks before the Iowa caucuses. The judge is expected to set a date next week, with Trump's team likely to push for a post-election trial. The Manhattan case is due to start in March, while the Florida judge in the classified documents affair has walled off May. These dates could slip, both as pre-trial litigation plays out and as judges and prosecutors potentially seek to accommodate one another. But the coming months in court will create pressure on Trump's time, his lawyers and his campaign.

Trump's team has warned that he can't get a fair trial while running for president -- a claim for which judges, so far, appear to have little time. But it's not hard to see that sooner or later, the realities of being a criminal defendant are likely to grate on the GOP front-runner.

In a dramatic hearing on Friday, for instance, Judge Tanya Chutkan -- who is presiding over the federal election subversion case -- asked his lawyers to accept that some of the former president's expectations of free speech, including the practice of attacking potential witnesses on the campaign trail, would be constrained by the fact that he was awaiting trial. "The defendant's desire to conduct a campaign, to respond to political opponents, has to yield ... there are limits regardless of you know, I hate to say -- his day job?" Chutkan said. "I mean, this is a criminal case. The need for this criminal case to proceed in the normal order and protect witnesses and the integrity of the process means that there are going to be limits on the defendant's speech."

The exchange on the particular conditions of that case might stand as a metaphor for Trump's legal entanglements as a whole. There is no doubt that the court schedule will infringe his "day job" of running for president in an unprecedented complication for a presidential campaign. And because of that day job, American politics will be dragged through his legal drama in a way that could taint yet another general election in the eyes of millions of voters. Americans have never seen the spectacle of a front-running candidate seeking a nomination while under such a cloud.

And if Trump becomes the Republican nominee, he will potentially be vying for the presidency against an incumbent whose Justice Department is trying to put him on trial. (While Smith is a special counsel, he's ultimately still under the auspices of Attorney General Merrick Garland.)

This unique political equation was further complicated last week with the announcement that David Weiss, the Trump-appointed prosecutor investigating Hunter Biden, would become a special counsel himself. This followed the collapse of a plea deal, which would have addressed two tax misdemeanor charges and resolved a felony gun charge against the president's son, and means the case could head to trial. Such a development could be a huge political headache for the president as he seeks reelection. It could also play into an attempt by Republicans to portray Joe Biden and his family as corrupt and to claim his administration has intervened to offer the younger Biden preferential treatment that was not available to Trump, even though House Republicans -- who are investigating such claims -- have offered no proof of wrongdoing by the president.

While the scale of offenses allegedly committed by Trump and Hunter Biden are not comparable, the split screen of two legal imbroglios is allowing Republicans to blur the distinctions.

So far, Trump's indictments have only boosted his brand among Republican primary voters. And Trump, whose leadership PAC is spending millions of dollars to pay his legal bills and those of his associates, is launching new fundraising efforts ahead of a possible fourth indictment in Georgia this week. "This would mark the FOURTH time in nearly as many months that Crooked Joe and his accomplices set fire to the rule of law all in the name of 'getting Trump,'" the ex-president wrote in an email solicitation from the Trump Save America Joint Fundraising Committee on Sunday.

A fourth indictment and multiple trials may not harm Trump in the primary, but they would raise questions about his already tarnished standing among swing and suburban voters, who will be important in a general election. It's too early to speculate how headlines about these cases could weigh on Trump or Biden in November 2024. But since their last duel came down to tens of thousands of votes in a handful of states, dramatic events taking place now could haunt either of them next year.