WASHINGTON >> As President Joe Biden pushes to vaccinate as many Americans as possible, he faces deep skepticism among many Republicans, a group especially challenging for him to persuade.

While there are degrees of opposition to vaccination for the coronavirus among a number of groups, including African Americans and anti-vaccine activists, polling suggests that opinions in this case are breaking substantially along partisan lines.

A third of Republicans said in a CBS News poll that they would not be vaccinated — compared with 10% of Democrats — and another 20% of Republicans said they were unsure. Other polls have found similar trends.

With the Biden administration readying television and internet advertising and other efforts to promote vaccination, the challenge for the White House is complicated by perceptions of former President Donald Trump’s stance on the issue. Although Trump was vaccinated before he left office and urged conservatives last month to get inoculated, many of his supporters appear reluctant to do so, and he has not played any prominent role in promoting vaccination.

Asked about the issue on Monday at the White House, Biden said Trump’s help promoting vaccination was less important than getting trusted community figures on board.

“I discussed it with my team, and they say the thing that has more impact than anything Trump would say to the MAGA folks is what the local doctor, what the local preachers, what the local people in the community say,” Biden said, referring to Trump’s supporters and campaign slogan “Make America Great Again.” Until everyone is vaccinated, Biden added, Americans should continue to wear masks.

Widespread opposition to vaccination, if not overcome, could slow the United States from reaching the point where the virus can no longer spread easily, setting back efforts to get the economy humming again and people back to a more normal life. While the problem until now has been access to relatively tight supplies of the vaccine, administration officials expect to soon face the possibility of supply exceeding demand if many Americans remain reluctant.

But many conservative and rural voters continue to point to a variety of worries. Some conservatives harbor religious concerns about the Johnson & Johnson vaccine, which uses abortion-derived fetal cell lines.

Republicans often cite distrust of government as a reason not to be vaccinated, the CBS poll found. They worry the vaccines were produced too quickly. And in some communities, so many people have already had the coronavirus that they think they have developed herd immunity and do not need the shots.

Other supporters of Trump believe Democrats exaggerated the toll of the pandemic to hurt the former president.

That presents a major challenge to a Democratic administration whose success depends on persuading Americans who did not vote for Biden to trust that the vaccines are safe, effective and necessary.

“We are not always the best messengers,” Jen Psaki, the White House press secretary, said last week.

That has meant outsourcing a crucial piece of the administration’s coronavirus response.

“It’s not an easy undertaking,” said John Bridgeland, a founder and the CEO of the COVID Collaborative, a bipartisan group of political and scientific leaders working on vaccine education, who has regular meetings with the White House on the issue of vaccine hesitancy.

“The good news is the White House has been all over all these populations, including recognizing that they’re not beautifully positioned to reach conservatives,” he said. “That’s why they’re reaching out to us and others.”

Governors have pressed the Biden administration on the need for clear communication about the vaccines.

White House officials said their research showed that making the vaccines more accessible and having local buy-in from doctors and pharmacists was the best way to sway skeptical conservatives to sign up for a shot. They are planning an advertising blitz on television, radio and the internet to target problem areas: young people, people of color and conservatives, an administration official said.

Even as they are working to ramp up vaccine availability across the country, administration officials are also working with groups like the NTCA — the Rural Broadband Association and the National Farmers Union to reach rural communities on their behalf.

Trump got his vaccine in secret before leaving office. He was notably absent from a public service announcement featuring all of the other former living presidents — Barack Obama, George W. Bush, Bill Clinton and Jimmy Carter — getting vaccinated and encouraging others to follow suit.

Trump was not asked to participate, as the others were, because at the time it was filmed, during Biden’s inauguration, he had not yet disclosed that he had been vaccinated.

But behind the scenes, there has been a quiet effort to persuade Trump to get involved. Joe Grogan, the former director of the White House’s Domestic Policy Council, under Trump, has been working with the COVID Collaborative on addressing vaccine hesitancy among conservatives.

Grogan has fielded calls about what the best message would be to take to Trump to persuade him to get involved — one that would inevitably underscore his desire for credit for developing the vaccines under Operation Warp Speed.

“As soon as we found out he was vaccinated, I reached out to Joe Grogan,” said Bridgeland, who helped organize the commercial featuring the former presidents. “We were thrilled he got vaccinated and very much want him to encourage his supporters to get the vaccine.”

A Trump adviser said the former president had not yet been approached in any formal way to speak directly to his supporters.

“Having President Trump doing a public service announcement would be very helpful,” Grogan said.

The Biden White House, however, appears split on how effective Trump’s involvement would really be.

Although Biden appeared dismissive on Monday of the need for Trump’s help, his chief medical adviser, Dr. Anthony S. Fauci, said Sunday on Fox News that it would “make all the difference in the world” if the former president would encourage his supporters to get vaccinated. And Andy Slavitt, a senior White House pandemic adviser, said on Sunday that “this is an effort, the Republicans should know, began before we got here, and we are carrying it out.”

Frank Luntz, a Republican strategist, said the best course for the White House would be to take the politics out of the issue.

“That means Joe Biden should be acknowledging what Donald Trump did to speed the vaccine to fruition,” Luntz said. He has been working with the de Beaumont Foundation, an organization focused on improving public health through policy, to help encourage conservatives to get vaccinated.

“I don’t believe the Trump administration understood the role of communication,” Luntz said, “and I don’t think the Biden administration understands what it means to communicate to Trump voters.”

On Saturday, Luntz hosted a focus group of about 20 conservatives to hear from Tom Frieden, the former head of the Centers for Disease Control and Prevention; Chris Christie, the former governor of New Jersey; and multiple Republican members of Congress.

Some of the conservatives on the call initially described the vaccines as “rushed” and “experimental” and the coronavirus as “opportunistic” and “government manipulation.” More than half of those on the call said their fears of getting vaccinated were greater than their fears of the virus.

But nearly everyone on the call said they had a more positive view on the vaccines after Frieden gave them five facts about the virus, including, “The more we vaccinate, the faster we can get to growing the economy and getting jobs.”

For now, the White House is relying on the work of political adversaries like Christie to sell the message for them. The one surrogate from inside the Biden administration that they view as effective among conservatives is Dr. Francis Collins, the director of the National Institutes of Health, who is a scientist and an evangelical Christian with standing in both religious and scientific communities.

In recent weeks, Collins has appeared on the Christian Broadcasting Network’s “700 Club,” a show popular among evangelical Christians that for decades has been hosted by Pat Robertson. Collins is also planning to address the National Association of Evangelicals, according to someone familiar with the planning.