Trump's campaign implied Iran was behind the move as news outlet Politico reported it had received emails with the campaign material from a source who refused to identify themselves.

"These documents were obtained illegally from foreign sources hostile to the United States, intended to interfere with the 2024 election and sow chaos throughout our Democratic process," Trump campaign spokesman Steven Cheung said in a statement.

Cheung cited a report from Microsoft this week that said Iranian hackers "sent a spear phishing email in June to a high-ranking official on a presidential campaign."

The materials received by Politico included research on vetting Vance, Trump's vice presidential pick.

In 2016, a hack of Democratic National Committee emails -- blamed on Russians -- exposed internal party communications, including about candidate Hillary Clinton.

Trump, who would go on to win the election, was criticized for encouraging the hack.