Let me continue from my link the Trumpies were too cowardly to read.
Claim 2: Russia has tried for years to manipulate Trump using lucrative business deals, and Russian operatives have collected compromising information that could potentially be used to blackmail Trump.
Evidence: These allegations are based on a 35-page dossier of opposition research on Trump, prepared by a former British intelligence officer hired by Trump’s Republican and Democratic rivals during the election. The dossier contained numerous explosive but
unverified claims.
The man who prepared the original 35-page dossier,
Christopher Steele, is respected for his intelligence work, particularly in Russia. However, because the claims remain uncorroborated, they should be viewed with skepticism.
The dossier circulated among Washington lawmakers, intelligence agents and journalists for months before becoming public knowledge, when unnamed U.S. officials told
CNN in January 2017 that intelligence officers presented Trump with a summary of the document.