WASHINGTON — The guilty plea of a 30-year-old campaign aide — so green that he listed Model United Nations in his qualifications — shifted the narrative on Monday of the Trump campaign’s interactions with Russia: Court documents revealed that Russian officials alerted the campaign, through an intermediary in April 2016, that they possessed thousands of Democratic emails and other “dirt” on Hillary Clinton.

That was two months before the Russian hacking of the Democratic National Committee was publicly revealed and the stolen emails began to appear online. The new court filings provided the first clear evidence that Trump campaign aides had early knowledge that Russia had stolen confidential documents on Mrs. Clinton and the committee, a tempting trove in a close presidential contest.

By the time of a crucial meeting in June of last year, when Donald Trump Jr. and other senior Trump campaign officials met with a Russian lawyer offering damaging information on Mrs. Clinton, some may have known for weeks that Russia had material likely obtained by illegal hacking, the new documents suggested. The disclosures added to the evidence pointing to attempts at collaboration between the Trump campaign and the Russian government, but they appeared to fall short of proof that they conspired in the hacking or other illegal acts.