The panel detailed how associates of the Republican candidate had regular contact with Russians and expected to benefit from the Kremlin’s help.
The report, the fifth and final one from the Republican-led Senate intelligence committee on the Russia investigation, describes how Russia launched an aggressive, wide-ranging effort to interfere in the election on Donald Trump’s behalf.
It says Trump associates were eager to exploit the Kremlin’s aid, particularly by maximising the impact of the disclosure of Democratic emails that were hacked by Russian military intelligence officers.
The report from the Republican-led panel lays out significant contacts between Trump associates and Russians, describing for instance a close professional relationship between Trump campaign chairman Paul Manafort and Konstantin Kilimnik, whom the committee describes without equivocation as a Russian intelligence officer.
The report notes how Mr Manafort shared internal Trump campaign polling data with Mr Kilimnik and says there is “some evidence” that Mr Kilimnik may have been connected to the Kremlin’s operation to hack and leak Democratic emails, though it does not describe that evidence.
The most comprehensive description to date of Russia’s activities and the threat they posed
In addition, the report says that “two pieces of information” raise the possibility of Mr Manafort’s potential connection to those operations, but what follows next in the document is blacked out.
Both men were charged in special counsel Robert Mueller’s Russia investigation, but neither was accused of any tie to the hacking.
A Manafort lawyer, Kevin Downing, said on Tuesday that there is information that was sealed at the request of Mr Mueller’s team “that completely refutes whatever the intelligence committee is trying to surmise”.
He added: “It just looks like complete conjecture.”
The Senate panel described its report, totalling more than 1,300 pages, as “the most comprehensive description to date of Russia’s activities and the threat they posed.”
The bipartisan investigation lasted almost three-and-a-half years, much longer than the other probes.
The report purposely does not come to a final conclusion, as the other reports did, about whether there is enough evidence that Trump’s campaign co-ordinated or colluded with Russia to sway the election to him and away from Democrat Hillary Clinton, leaving its findings open to partisan interpretation.
A group of Republicans on the panel submitted “additional views” to the report, saying that it should state more explicitly that Trump’s campaign did not co-ordinate with Russia.
But Democrats on the panel submitted their own views, arguing that the report clearly shows such co-operation.
Mr Mueller concluded in a report issued last year that Russia interfered in the election through hacking and a covert social media campaign, and that the Trump campaign embraced the help and expected to benefit from it, but Mr Mueller did not charge any Trump associates with conspiring with Russians.
The Senate investigation also delved into areas of great interest to Mr Trump that were not explored by Mr Mueller.
Those include the FBI’s reliance on a dossier of opposition research compiled by a former British spy whose work was financed by Democrats.
Senator Marco Rubio, the committee’s acting chairman, said in a statement that the committee was troubled that the FBI had been willing to use the dossier “without verifying its methodology or sourcing” as it applied for secret surveillance warrants against a former Trump campaign adviser.
