Biden’s approval rating rises, helped by the vaccine distribution push.

The American public doesn’t think President Biden deserves sole credit for the widespread availability of Covid-19 vaccines, but it overwhelmingly likes the job he’s doing getting them distributed — and it’s feeding a high job approval rating over all.

Those are among the results of a Pew Research Center poll released on Thursday that offers a portrait of a country that is increasingly positive about its political leaders.

As Mr. Biden nears his 100th day in office, his approval rating stood at 59 percent, according to the poll, with 39 percent of respondents disapproving of his performance in office. That’s a small but meaningful uptick from his 54 percent approval in a Pew poll last month.

In the most recent survey, two-thirds of the country approved of the $1.9 trillion Covid-19 aid package that Mr. Biden recently signed, though approval cleaved hard to party lines. Forty-nine percent of all respondents said they expected the package to have a positive effect on them and their family; just 14 percent thought it would affect them negatively.

The president got particularly high marks with regard to managing and distributing coronavirus vaccines. Seventy-two percent of Americans said his administration had done this well, including 55 percent of Republicans and independents who lean toward the G.O.P., according to the poll.

The public gives Mr. Biden’s predecessor some credit for helping to make vaccines available: 55 percent said the Trump administration had done a good or excellent job supporting the development of coronavirus vaccines. But fewer, 43 percent, said the Trump White House had been successful when it came to getting the vaccines made and distributed.

Forty-four percent of respondents said Mr. Biden had changed the “tone and nature” of the political discourse for the better, while just 29 percent said he had made them worse. Republicans were an exception, with 62 percent saying he had altered the conversation for the worse and 11 percent saying for the better.

Americans’ increasingly positive views about the politicians in Washington extended to their representatives in Congress. For the first time in almost two decades, half of Americans expressed approval of the job that congressional Democrats were doing, while 47 percent disapproved.

Americans’ views of their representatives in Washington have long been rather dismal, and for congressional Republicans, public approval remains deeply negative: Just 32 percent approved of their performance.

Over all, just 36 percent of the country expressed a generally favorable opinion of Congress. Still, that was as high as it has been at any point in the past decade.

Asked for their thoughts on 15 political and social issues, respondents were most likely to rate the affordability of health care as a very serious problem, according to the poll. Fifty-six percent said so, with another 30 percent saying it was a moderately big problem.

The Biden administration has not put health care at the top of its priorities list, partly an acknowledgment of how thorny the issue has been for previous presidents, and of how divided Democrats remain on whether to push for a single-payer system.

But concerns about health costs decisively outpaced other issues, including the federal debt (49 percent), illegal immigration (48 percent), gun violence (48 percent) and the coronavirus outbreak (47 percent) in terms of the share of Americans calling the matter a big issue.

The poll was conducted from April 5 to 11 and reached 5,109 respondents via Pew’s American Trends Panel, which uses a probability-based model to draw a sample that is representative of the national population.