washington political research firm prepare dossier trump campaign tie russia unrelated information clinton foundation donors russian lawyer obtain offer president donald trump eldest son last year three source familiar matter say white house republican lawmakers attack firm fusion gps dossier compile former british spy central investigations congress special counsel conclusions u.s. spy agencies moscow interfere 2016 presidential election want help trump win source tell reuters negative information russian lawyer natalia veselnitskaya want give republican trump campaign june 2016 meet new york dig fusion gps unrelated investigation trump congressional supporters suggest fusion also conduct research lawyers represent russian firm unrelated matter dossier part russian campaign help democratic candidate hillary clinton trump backers call 35-page report dodgy dossier finance clinton supporters russia repeatedly deny allegations meddle u.s. election trump deny collusion campaign moscow officials interview bloomberg monday veselnitskaya say go trump tower meet donald trump jr. brother-in-law jar kushner top campaign adviser paul manafort show proof tax evasion major democratic donors say donald jr. ask write evidence illegal fund go clinton campaign bloomberg report email make public early year trump jr. show publicist son one father russian business contact help introduce veselnitskaya advise associate sensitive information could damage clinton love trump jr. respond accord email december 2014 source say veselnitskaya involve litigation pit russian client british-american financier william browder receive legal research memo report ziff brothers two new york financier ally browder make large contribution clinton charity memo prepare fusion hire conduct legal research browder baker hostetler law firm firm represent russian businessman denis katsyv engage dispute browder u.s. prosecutors glenn simpson one fusion gps founder meet veselnitskaya litigation meet trump jr. kushner manafort accord source familiar matter however source familiar 10 hours testimony simpson give senate judiciary committee august say tell investigators know veselnitskaya trump tower meet report appear media representatives judiciary committee republican majority respond request comment spokesman manafort decline comment representatives trump jr. kushner could immediately reach comment neither could u.s.-based lawyer veselnitskaya two source say fusion gps work baker hostetler produce information veselnitskaya offer trump jr. associate unrelated firm work perkins coie law firm represent democratic national committee clinton campaign perkins coie acknowledge pay 1.02 million fusion research relate donald trump campaign trump clinton camp offer slice dossier firm 's work source