WASHINGTON (Reuters) - The top Democrat on the Senate Intelligence Committee said on Thursday that testimony by fired FBI Director James Comey showed President Donald Trump appeared to threaten his job and asked him to drop an investigation into a senior aide, violating clear guidelines designed to prevent political interference into FBI probes. “The testimony that Mr. Comey has submitted for today’s hearing is disturbing,” Mark Warner will say in his opening statement at a committee hearing, according to excerpts obtained by Reuters.  (Refiles to corrects day of week in first paragraph.) 