News that special counsel Robert Mueller ended his investigation without recommending criminal charges against President Donald Trump has had little effect on public opinion, a new NBC News/Wall Street Journal poll shows.

The proportion of Americans who say the investigation has not increased their doubts about the Trump administration rose by 10 points to 57 percent in the survey, while the proportion who say it has increased their doubts fell 12 points to 36 percent since February. But the president's job approval dropped by three points to 43 percent during the same period.

Behind those offsetting results is the fact that Americans have not been nearly as attuned to news about the Mueller investigation as the political and media worlds have been. Just 39 percent said they had read or heard "a lot" of news coverage of the end of the probe.

"It was not an event that captured the American public," said Republican pollster Bill McInturff, who conducts the NBC/WSJ poll with his Democratic counterpart Peter Hart.

So far, only Attorney General William Barr's four-page summary of Mueller's nearly 400-page report has been publicly released. Barr has promised to release the bulk for the report by mid April, but for now Americans are withholding definitive judgment.

In the survey, 29 percent said they though Mueller had cleared Trump of wrongdoing, while a 40 percent plurality said he had not. Another 31 percent weren't sure.

And Americans remain split on the prospect of impeachment proceedings. Sixteen percent of the public see enough evidence to begin impeachment hearings now, while another 33 percent say Congress should investigate before deciding the matter. Another 47 percent want Congress to eschew impeachment and allow Trump to complete his term.

Should the president seek re-election to a second term, he'd begin with a solid base of support but a larger group of voters with misgivings about his candidacy. The poll showed 40 percent of Americans would feel enthusiastic or comfortable about supporting him, while 59 percent would have reservations or be very uncomfortable.

Opinion divides more evenly on former Vice President Joe Biden. As he considers whether to enter the race, 47 percent say they'd feel enthusiastic or comfortable backing him, while 48 percent would not.

The early profile of Vermont Sen. Bernie Sanders on this measure, 37 percent vs. 58 percent, resembles Trump's. Sen. Elizabeth Warren of Massachusetts has a similar standing at 30 percent vs. 51 percent.

Democratic contenders Sen. Kamala Harris of California and former Rep. Beto O'Rourke of Texas remain less well known. Both discomfort four in 10 Americans at this stage, while roughly one in four feel positively about their candidacies.

The telephone survey of 1,000 adults, conducted March 23-27, carries a margin for error of 3.1-percentage points.