washington top democrats u.s. senate house representatives intelligence committees call wednesday white house consider declassify release intelligence community assessments hack democratic national committee email system experts attribute breach russian hackers give grave nature breach fact may ultimately find state-sponsored attempt manipulate presidential election believe heighten measure transparency warrant senator dianne feinstein representative adam schiff write letter president barack obama obama say interview broadcast nbc news tuesday federal bureau investigation investigate leak 19,000 dnc email show committee favor hillary clinton bernie sanders party presidential nomination senior u.s. lawmakers want information dnc hack declassify