WASHINGTON — Less than a month into President Donald Trump’s tenure, an overwhelming share of Americans already have strongly held views about his job performance and positions are deeply polarized.

Trump’s core supporters continue to strongly back the new president, a survey from the nonpartisan Pew Research Center finds. His opponents — a larger group — fervently disapprove of him.

Those polarized views help explain why Trump’s attacks on the media and repeated mentions of his defeated Democratic opponent — he mentioned “Hillary” 12 times during his news conference Thursday — may make sense as a strategy. While his approach may not change the minds of people who dislike him, it could help rally his existing supporters.

The Pew survey found that three-quarters of Americans either strongly approve or strongly disapprove of Trump. That’s a much higher number than had strongly held views of other presidents at this stage of their terms in office.

Overall, the survey, which was conducted last Tuesday through Sunday, found that 56 percent of Americans disapproved of Trump’s performance in office and 39 percent approved.

That marked the first major poll in which Trump’s approval dropped below 40 percent, but it’s only slightly lower than several other recent polls.

The finding does, however, differ a lot from the poll by Rasmussen, a Republican favorite, which Trump cited in his news conference. That survey found 55 percent of Americans approving of Trump’s performance in office.

One major difference between the surveys is that Rasmussen, alone among recent major surveys, reported numbers only from people it considered “likely voters” — a hard group to define this far away from an election and one that can easily be skewed.