A declassified intelligence assessment found broad efforts by the Kremlin and Iran to shape the outcome of the race.
However, ultimately no evidence was found of any foreign actor changing votes or otherwise disrupting the voting process.
The report released on Tuesday from the Office of the Director of National Intelligence represents the most detailed assessment of the array of foreign threats to the 2020 election.
These included efforts by Iran to undermine confidence in the vote and harm Mr Trump’s re-election prospects as well as Moscow operations that relied on the former president’s allies to smear Joe Biden, the eventual winner.
Despite those threats, though, intelligence officials found “no indications that any foreign actor attempted to interfere in the 2020 US elections by altering any technical aspect of the voting process, including voter registration, ballot casting, vote tabulation, or reporting results.”
The report is the latest official affirmation of the integrity of the election, even as Trump supporters continue to make false claims of interference, from foreign or domestic actors, and refuse to accept Mr Biden’s victory.
Multiple courts and even Mr Trump’s own Justice Department refuted claims of widespread fraud.
The document makes clear that even while Mr Trump has cried foul about the legitimacy of the election, intelligence officials believe Russia sought to influence people close to Mr Trump as a way to tip the election in his favour.
The report wades into the politically charged task of ferreting out which foreign adversaries supported which candidates during the 2020 election, an issue that dominated headlines last year.
Mr Trump’s 2016 campaign benefited from hacking by Russian intelligence officers and a covert social media effort.
He seized on an intelligence assessment from August that said China preferred a Mr Biden presidency — even though the same assessment also said Russia was working to boost Mr Trump’s own candidacy by disparaging Biden.
Tuesday’s report, however, says China ultimately did not interfere on either side and “considered but did not deploy” influence operations intended to affect the outcome.
US officials said they believe Beijing prioritised a stable relationship with the US and did not consider either election outcome as advantageous enough for it to risk the “blowback” that would ensue if it got caught with interfering.
The primary threats instead came from Russia and Iran, albeit with different intentions and through different means, according to intelligence officials.
The report said Russia sought to undermine Mr Biden’s candidacy because it viewed his presidency as opposed to the Kremlin’s interests, though it took some steps to prepare for a Democratic administration as the election neared.
The report also says Putin authorised influence operations aimed at denigrating Mr Biden, boosting Mr Trump, undermining confidence in the election and exacerbating social divisions in the US.
Central to that effort was reliance on proxies linked to Russian intelligence “to launder influence narratives” by using media organisations, US officials and people close to Mr Trump to push “misleading or unsubstantiated” allegations against Mr Biden.
Iran, meanwhile, carried out its own influence campaign aimed at harming Mr Trump’s re-election bid, an effort US officials say was probably approved by Supreme Leader Ayatollah Ali Khamenei.
One “highly targeted operation” involved a flurry of emails to Democratic voters in battleground states that falsely purported to be from the far-right group Proud Boys and threatened the recipients if they didn’t vote for Mr Trump.
Iran’s efforts, which officials said were more aggressive than in past elections and continued even after the contest was over, were focused on sowing discord in the US, likely because Tehran believed that would hurt Mr Trump’s re-election chances.
Though Iran sought to exploit vulnerabilities on state election websites, and did “compromise US entities associated with election infrastructure as a part of a broad targeting effort across multiple sectors worldwide,” it did not attempt to manipulate votes or affect election infrastructure, the report concluded.
The 15-page document is a declassified version of an election interference report that was provided to Mr Trump on January 7 – one day after a riot at the US Capitol that occurred as Congress was gathering to certify the election results.
A separate document released on Tuesday from the departments of Justice and Homeland Security reached a similar conclusion about the integrity of the election, saying there was no evidence any foreign actor had changed votes.