Assange's team said during a pre-extradition hearing in London that Republican congress member Dana Rohrabacher "acted as an emissary for the White House" and offered the deal in 2017, per the Daily Beast's report. Notably, that means the alleged offer occurred one year following the publication of Clinton-damaging emails that had been lifted from the DNC.
Current White House press secretary Stephanie Grisham shared a statement on the allegations, claiming that Trump "barely knows" Rohrabacher. Grisham further claimed Trump has "never spoken to him on this subject or almost any subject." Assange's team, however, said Wednesday that they have evidence. Assange's extradition hearing is set to begin on Feb. 24.
Back in 2017, as the Guardian noted in a separate report, the White House confirmed that Rohrabacher had contacted (now former) chief of staff John Kelly to discuss a possible Assange deal that allegedly included the handing over of a computer drive or similar device that would then be used to "prove that Russia was not the source" of the WikiLeaks-published emails.
Furthermore, Rohrabacher once recalled what he claimed was a drunken bout of arm-wrestling with Vladimir Putin, the president of Russia.