President-elect Donald Trump would have been convicted of illegally trying to overturn the result of the 2020 presidential election – which he lost – if he had not successfully been re-elected in 2024, according to the man who led US government investigations into him.

The evidence against Trump was “sufficient to obtain and sustain a conviction at trial,” Special Counsel Jack Smith wrote in a partially released report.

Trump hit back, saying Smith was “deranged” and his findings were “fake”.

Trump was accused of pressurising officials to reverse the 2020 result, knowingly spreading lies about election fraud and seeking to exploit the riot at the US Capitol on 6 January 2021. He denied any wrongdoing.

Trump, who was president at the time of the alleged crimes, subsequently spent four years out of office – but was successfully re-elected to the White House in November. He will return to the presidency next week.

After his success in the 2024 vote, the various legal issues that he had been battling have largely evaporated. The interference case has now been dismissed.

Smith says in the report he “stands fully behind” the merits of bringing the prosecution and the strength of the case.

He went on to say it was only the fact the US Constitution forbids the prosecution of a sitting president that ended it.

“But for Mr Trump’s election [in 2024] and imminent return to the presidency, the office assessed that the admissible evidence was sufficient to obtain and sustain a conviction at trial.”

Some of the material in Smith’s report was already known thanks to a public filing in October, which gave details of Trump’s alleged efforts to overturn his defeat.

But the report, which was released by the Department of Justice (DoJ) to Congress, gives further detail on why Smith pursued the case, and ultimately closed it.

• It justifies the case against Trump by accusing him of “unprecedented efforts to unlawfully retain power” through “threats and encouragement of violence against his perceived opponents”
• Running through Mr Trump’s “criminal efforts” were election fraud claims he knew to be false, it says
• The report details “significant challenges” faced by investigators, including Trump’s use of social media to target witnesses, courts, and justice department employees
• Denying the case was politically motivated, Smith says: “The claim from Mr Trump that my decisions as a prosecutor were influenced or directed by the [President Joe] Biden administration or other political actors is, in a word, laughable”
• Smith further reflects in the accompanying letter: “While we were not able to bring the cases we charged to trial, I believe the fact that our team stood up for the rule of law matters”

The 137-page document was sent to Congress after midnight on Tuesday, after a period of legal jostling that culminated in a judge clearing the way for the first part of Smith’s report to be released.

The judge, Aileen Cannon, ordered a hearing later in the week on whether to release the second part of the report – which focuses on separate allegations that Trump illegally kept classified government documents at his home in Florida.

Posting on his Truth Social website, Trump maintained his innocence, taunting Smith by writing that the prosecutor “was unable to get his case tried before the election, which I won in a landslide”.

Trump added: “THE VOTERS HAVE SPOKEN!!!”

Smith was appointed in 2022 to oversee the US government investigations into Trump. Special counsels are chosen by the DoJ in cases where there is a potential conflict of interest.

In the interference case, Trump was accused of conspiring to overturn the result of the 2020 election, which he lost to Joe Biden.

Both this case and the separate classified documents case resulted in criminal charges against Trump, who pleaded not guilty and sought to cast the prosecutions as politically motivated.

But Smith closed the cases after Trump’s election in November, in accordance with DoJ regulations that forbid the prosecution of a sitting president.

The report explains: “The department’s view that the [US] Constitution prohibits the continued indictment and prosecution of a president is categorical and does not turn on the gravity of the crimes charged, the strength of the government’s proof, or the merits of the prosecution, which the office stands fully behind.”

It adds that prosecutors found themselves at a crossroads: “The [2024] election results raised for the first time the question of the lawful course when a private citizen who has already been indicted is then elected president.”

Tuesday’s release comes after a period of legal back-and-forth, during which Judge Cannon put a temporary stop on releasing the whole Smith report, over concerns that it could affect the cases of two Trump associates charged with him in the separate classified documents case.

Walt Nauta, Trump’s personal aide, and Carlos De Oliveira, the property manager at Mar-a-Lago, are accused of helping Trump hide the documents.

Unlike Trump’s, their cases are still pending – and their lawyers argued that the release of Smith’s report could prejudice a future jury and trial.