While presidents have been deposed in criminal matters, impeached and pardoned, and their family members entangled in legal scrapes before, never has the criminal courtroom taken center stage in a presidential election like this.

"It's so unusual that we lack the terminology to express how unusual it is," said presidential historian Lindsay Chervinsky, author of the upcoming book, "Making the Presidency: John Adams and the Precedents That Forged the Republic."

The two criminal cases are in no way the same. One involves the conduct of a former president who is running to reclaim the White House, yet stands accused of falsifying business records to conceal an illegal scheme to influence the 2016 election. The other focuses on a private citizen -- albeit the current president's son -- who is facing charges of lying on a federal gun-purchase form when he claimed he wasn't using drugs.

Politically, though, there is some obvious overlap. Both men say they're being persecuted by overzealous prosecutors and unfairly targeted for political gain. And both sides are seeking to capitalize on highly personal and potentially embarrassing witness testimony about their adversaries, with Republicans trying to use Hunter Biden as a sort of target by proxy for the president himself.

The politics of the moment

Trump has leaned hard into the politics of the moment, campaigning from court, claiming he's the subject of a "witch hunt" and casting doubt on the validity of the nation's criminal justice system. Biden, for his part, has largely steered clear, a purposeful effort to highlight the independence of the judiciary.

But this week, Biden's campaign decided that Trump's case -- the first of four criminal cases and quite possibly the only one to go to trial before the 2024 election -- couldn't be ignored any longer. The campaign brought in actor Robert De Niro and law enforcement officers who had defended the U.S. Capitol during the insurrection on Jan. 6, 2021, to denounce Trump in a press conference near the lower Manhattan courthouse.

Biden campaign spokesman Michael Tyler said the press conference was called because reporters are "incessantly covering this day in and day out."

"And we want to remind the American people ahead of the first debate on June 27, of the unique, persistent and growing threat that Donald Trump poses to the American people and to our democracy," he said.

Trump's operation was quick to follow team Biden to the same bank of microphones to deride the press conference as evidence of "a desperate and failing and pathetic campaign who knows that they are losing," in the words of Trump campaign spokeswoman Karoline Leavitt.

Inside, meanwhile, jurors were hearing closing arguments in Trump's hush money trial.

Trump's trial is ending

Prosecutors say Trump and his allies mounted a campaign to purchase and squelch potentially embarrassing stories, and cover up those payments in an illegal effort to influence voters in the waning weeks before the 2016 presidential election, particularly as Republicans grew concerned over potential fallout from the "Access Hollywood" tape in which Trump bragged about grabbing women sexually without their permission.

To help make their case to jurors, prosecutors relied on checkered characters from Trump's orbit including porn actor Stormy Daniels, who testified about an alleged sexual encounter with Trump. The prosecution's most important witness was Trump's former lawyer- turned-foe Michael Cohen, who paid off Daniels and who placed Trump at the center of the scheme he denies.

Throughout, Trump has strategically positioned prominent allies in the audience of the courtroom and used the trial as a fundraising pitch. These allies have held press conferences in a small park nearby where they decry the criminal justice system. Trump's family, too, has appeared in court.

Hunter Biden's trial is beginning

In contrast, Hunter Biden has been largely on his own in public to face his legal problems.

Republicans have relentlessly dug into his personal life, struggles with addiction and business dealings, trying -- unsuccessfully -- to link those dealings to the president. Hunter Biden was silent for years amid GOP criticism. But as his case looms, he has gone on the offense, arguing publicly that he's being unfairly targeted.

President Biden has said he loves his son and doesn't generally comment on the details of his son's case. But the president has already been put in the unusual if not awkward position of ruling out a pardon should his son be convicted. He is scheduled to head to France for a D-Day commemoration as Hunter Biden's case begins.

White House aides say they're concerned about the toll the trial will take on the president and first lady, who remain deeply concerned about the health, well-being and sobriety of their son. Privately, some Democrats have expressed concern that Hunter Biden's legal problems could harm the president's reelection campaign and even pose difficulties for Democrats in tight House races.

White House press secretary Karine Jean-Pierre said Tuesday the president was focused on the American people, not the trials.

"The president and the first lady, they love their son. They are proud of how their son has been able to get back on his feet and continue his progress and will continue to support him," she said.

Hunter Biden pleaded not guilty to tax and gun charges after a plea deal collapsed last year that would have spared him -- and his father -- the spectacle of a trial. His defense attorney Abbe Lowell has argued prosecutors then "buckled under political pressure" to indict the president's son as Republicans and Trump rained down criticism of the proposed plea deal and claimed the younger Biden was getting special treatment.

The proposed list of questions for prospective jurors includes: "Raise your hand if you do not believe in this statement: The law should apply equally to all, including the son of the president."

The case against Hunter Biden stems from a period where, by his own public admission, he was addicted to crack. His descent into drugs and alcohol followed the 2015 death of his brother Beau Biden from cancer. Hunter Biden bought and owned a gun for 11 days in October 2018, and indicated on the gun purchase form that he was not using drugs.

Prosecutors are planning to use as evidence Hunter Biden's published memoir, and they may also introduce contents from a laptop that he left at a Delaware repair shop and never retrieved. The contents made their way to Republicans in 2020 and were publicly leaked, revealing embarrassing and personal photos and messages.

They're also planning to call as witnesses Hunter Biden's ex-wife and his brother's widow Hallie, with whom he became romantically involved. Prosecutors hope to show he was in the throes of addiction when he bought the gun.

The court documents do not name them, but it's clear from context that "witness three" describes Hallie Biden, who saw Hunter Biden using drugs many times, and according to the court documents: "searched his bags, backpacks, and vehicle in an effort to help him get sober, and discovered drug paraphernalia and drugs in his possession on multiple occasions."

Biden visited Hallie Biden last weekend, prompting questions about whether they'd talked about the upcoming case.

Jean-Pierre said the visit was "not about that," but rather about the approaching anniversary of Beau's death.

___ Associated Press writer Alanna Durkin Richer in Washington contributed to this report.