NBC’s poll of 800 adults was conducted Thursday through Saturday and has a 3.5 percent margin of error.
Gallup’s poll of 1,013 adults was conducted Wednesday and Thursday and has a 4 percent margin of error.
The latest RealClearPolitics.com average of all polls shows 41.5 percent approve of Trump's performance, while 53.4 percent disapprove.
The most Trump-friendly poll, Rasmussen Reports, found 45 percent approved and 55 percent disapproved in its first survey after Comey's firing. In early May, Rasmussen found 49 percent of respondents approved and 51 percent disapproved of Trump's job performance.