As the longest government shutdown in history nears its one-month anniversary, a new poll shows President Trump taking a significant hit among his base.

A survey from NPR/PBS NewsHour/Marist published Thursday found that Trump's approval rating is down among suburban men, white evangelicals, Republicans, and white men without a college degree. The most drastic change was among suburban men, 42 percent of whom approve of Trump while 48 percent disapprove, compared to 51 percent approval and 39 percent disapproval last month.

Additionally, among white evangelicals, Trump is down to 66-to-23 approval from 73-to-17 approval last month. Among Republicans, he's down to 83-to-10 percent approval from 90-to-7 percent last month. Finally, among white men without a college degree, he's down to 50-to-35 percent approval from 56-to-34 last month.

These are all demographics that brought Trump to victory in 2016. A CNN exit poll at the time, for example, suggested 71 percent of white men without a college degree voted for Trump. "For the first time, we saw a fairly consistent pattern of having his base showing evidence of a cracking ," Lee Miringoff, the director of Marist Institute for Public Opinion, told NPR about this new poll.

A previous poll by Morning Consult found that Trump's net approval rating is below zero in key states that he carried in 2016, including Ohio, Florida, Michigan, Pennsylvania, and Wisconsin.

NPR/PBS NewsHour/Marist's poll was conducted by speaking to 1,023 adults from Jan. 10-13. The margin of error is 3.8 percentage points. See more results at NPR. Brendan Morrow