The revelation that aides to Joe Biden discovered classified documents as they were moving boxes out of the president's Washington-based think tank offices already had the potential to be a political headache.
Now a second batch has been found at a different, undisclosed location, the embarrassment will deepen further.
It could also place him in legal jeopardy, although too little information is known about the documents and why they were not stored securely at the US National Archives to draw conclusions yet.
Mr Biden's critics are quickly drawing comparisons between these disclosures and the ongoing Department of Justice investigation into Donald Trump's handling of classified material following his departure from the White House in January 2021.
So how do the two compare?
The number, type and location of the files
According to news reports, Mr Biden's personal lawyers found 10 classified documents - some marked Top Secret - included in a box of other material in a storage closet at the University of Pennsylvania's Biden Center for Diplomacy and Global Engagement. That contrasts with the more than 325 classified files - including some marked with Secret and Top Secret designations - discovered over the course of last year at Mr Trump's Mar-a-Lago estate in Florida.
We don't know how many files were found in the second Biden cache.
The distinction between Mr Biden's think tank office and Mr Trump's personal residence could be a notable one, even if it is not entirely surprising given the former president's penchant for mixing business and personal affairs.
The documents discovered in Mr Biden's office were marked "sensitive compartmented information", according to CNN, indicating the material could involve intelligence-gathering methods and sources. They reportedly included information about Ukraine, Iran and the UK.
Of the 300 Trump documents recovered at Mar-a-Lago, one set had a similar SCI designation.
The origins of the investigations
According to Mr Biden's special counsel, his personal lawyers discovered the classified documents as they were moving out of the Biden Center's Washington offices on 2 November. The following day, they turned the material over to the National Archives.
We don't know how the second trove was found but it is being reported they were part of a search of all the offices Biden used, sparked by the think tank discovery.
In Mr Trump's case, the National Archives initiated contact with Mr Trump's office after determining that it did not have possession of some notable records from his presidential term - such as correspondence with North Korea's Kim Jong-un.
The former president's team conducted a review of his Mar-a-Lago storage facilities and provided the government with some material, including classified documents, but archivists did not believe the president's team had been fully co-operative. That set in motion the FBI inquiry that led to the August raid of the Mar-a-Lago estate and the discovery of more than 100 additional documents.
The matter has now been handed over to Justice Department Special Counsel Jack Smith, who is reportedly looking into whether Mr Trump or his team violated federal law by obstructing the document recovery process or destroying government materials.
The response to the missing documents
In the days after the Mar-a-Lago raid, Mr Trump accused the FBI and the Justice Department of pursuing a politically motivated investigation in an effort to prevent him from running for the White House again (a campaign he would subsequently launch in November).
Mr Biden, for his part, said Mr Trump's handling was "totally irresponsible".
Now that the president himself is being accused of mishandling classified information, Mr Trump has quickly gone on the offensive.
"When is the FBI going to raid the many homes of Joe Biden, perhaps even the White House?" he posted on his social media site.
Mr Biden has said that he was "surprised" there were sensitive documents at his former office and that he is co-operating fully with the review.
As more details emerge of the second discovery the president may have to offer a clearer explanation.
