No, Donald Trump's classified documents case is not like Joe Biden or Hillary Clinton cases

Almost immediately after the Justice Department on Friday unsealed its indictment against Donald Trump, the former president's allies began crying foul, noting that -- at least so far -- no charges have been filed against President Joe Biden for retaining classified documents from his time as vice president or against Hillary Clinton for her use of a private email server as secretary of state.

Posting to Twitter on Friday, House Speaker Kevin McCarthy, R-Calif., denounced the "double standard." And appearing on ABC's "This Week" on Sunday, Sen. Lindsey Graham, R-S.C., said Clinton "got away" with doing something "similar" to what Trump did.

Trump himself has made similar claims.

But a review of government documents and public statements tied to all three investigations suggests there are key differences between the evidence uncovered in Trump's case and the others. It also helps to explain why the Justice Department recently declined to charge former Vice President Mike Pence for his handling of classified documents after leaving office.

What's the intent?

The most glaring difference between Trump's case and Clinton's case is what prosecutors found about their intent: While the indictment against Trump alleges he violated the Espionage Act through "willful retention of national defense information," prosecutors in Clinton's case determined they couldn't show she was "willful" in her intent.

In fact, as later recounted by the Justice Department's inspector general, prosecutors in Clinton's case concluded the evidence they gathered showed "a lack of intent to communicate classified information on unclassified systems."

That's largely because "[n]one of the emails Clinton received were properly marked to inform her of the classified status of the information," and investigators found evidence that Clinton and her aides "worded emails carefully in an attempt to 'talk around' classified information," according to the inspector general's report on the matter.

"There was no evidence that the senders or former Secretary Clinton believed or were aware at the time that the emails contained classified information," prosecutors concluded, according to the inspector general.

By contrast, the indictment against Trump not only says that nearly all of the 31 documents he's charged with "willfully" retaining at his Mar-a-Lago estate were marked as classified, but it also details alleged conversations and actions showing that he allegedly knew he took and held onto classified documents from the White House.

In one recording obtained by investigators, Trump can be heard -- six months after leaving office -- showing a writer and three others what he calls a "secret" document, prosecutors allege. "As president I could have declassified it ... [but] now I can't," he said on the recording, according to the indictment.

Media reports say authorities have been unable to find that document. And Trump is not charged with illegally retaining it or nearly 200 other documents that were returned to the U.S. government before the Justice Department issued its subpoena to Trump.

Trump has insisted he's "an innocent man" who "did nothing wrong," claiming on social media after the indictment was unsealed that "this case has nothing to do with the Espionage Act."

In defending his actions detailed in the indictment, Trump has suggested he was operating in accordance with the Presidential Records Act -- an assertion that the National Archives has disputed.

Nevertheless, he noted on social media that "Hillary and Biden were not indicted" for their handling of sensitive documents.

'If Trump had done the same'

The indictment against Trump alleges that his "refusal to return" so many classified documents -- despite "months of demands" by the National Archives and a federal grand jury subpoena -- and the conspiracy he allegedly launched to "hide and conceal" his "continued possession of documents with classification markings" reflects his intent.

He participated in that conspiracy "knowingly and willfully," including by allegedly pushing his own attorney to lie to federal authorities seeking all classified documents and by allegedly directing one of his aides to hide certain boxes of documents from that attorney, according to the indictment.

"The purpose of the conspiracy was for Trump to keep classified documents he had taken with him from the White House," the indictment says.

By contrast, after Pence's team conducted a review of his own records and found "some classified documents" at his home in Indiana, Pence "fully cooperated with the Justice Department," according to Pence.

"I took full responsibility," Pence told conservative radio host Hugh Hewitt last week, just days after the Justice Department notified Pence that it would not be seeking charges in the matter. "[They] found that it was an innocent mistake."

In Clinton's case, she and her aides also largely cooperated in the FBI's investigation, according to the Justice Department's inspector general.

In his report, the inspector general said "the FBI obtained more than 30 devices" from Clinton and her aides, and "received consent to search Clinton-related communications on most of these devices." Among those 30 devices were two of Clinton's three private email servers, after the third server had been "discarded" years earlier "and, thus, the FBI was never able to access it for review," the inspector general's report said.

According to the indictment against Trump, the former president privately expressed admiration for how Clinton's lawyer handled her case, saying "she didn't get in any trouble because," as Trump described it, her lawyer took responsibility for deleting 30,000 emails that Clinton's legal team determined were personal in nature and not subject to government review.

But, according to the Justice Department's inspector general, the FBI was actually able to retrieve a majority of those deleted emails through the many devices it obtained and through other means.

As for Biden, the special counsel appointed by Attorney General Merrick Garland to investigate Biden's retention of classified documents from his time as vice president in the Obama administration has yet to announce his findings. But Biden's attorneys have insisted that from "the outset of this matter, the President directed his personal attorneys to fully cooperate with the Department of Justice."

When Biden's personal attorneys first found classified documents in private offices associated with Biden, they said they notified the National Archives and Records Administration, and they helped the government retrieve them, with one of Biden's attorneys writing in an email at the time, "[W]e are prepared to facilitate whatever access you need to accomplish NARA taking custody of whatever materials it deems appropriate."

And when the Justice Department then wanted to search Biden's home in Delaware, Biden and his attorneys granted "full access" to the president's residence, where investigators found additional documents marked classified, his lawyers said in a public statement at the time.

"If Trump had done the same, there would have been no grand jury, there probably would have been no search warrant, and [he] probably would have avoided a potential criminal problem," former Watergate prosecutor Nick Akerman previously told ABC News.

ABC News' Alexander Mallin and Luke Barr contributed to this report.