President Trump faces a significant challenge in his bid to win reelection in November, with former vice president Joe Biden holding a double-digit lead nationally and the president’s approval ratings crumbling amid a spreading coronavirus pandemic and a weakened economy, according to a Washington Post-ABC News poll.

The survey portrays an embattled president whose fortunes have declined markedly since the coronavirus arrived in the United States months ago. Trump’s prospects for winning in November appear to depend heavily on his ability to rally an enthusiastic core base of supporters and on convincing a broader swath of a largely skeptical public that he is dealing effectively with the pandemic.

Biden leads Trump 55 percent to 40 percent among registered voters. That compares with a 10-point Biden lead in May and a two-point edge in March, at a time when the pandemic was just beginning to spread rapidly in parts of the country. Among those who say they are certain to vote, Biden’s lead stands at 11 points.

Despite the president’s attempts to shift the electorate’s focus to his criticisms of Biden, both candidates’ supporters are treating the November election as a referendum on Trump. Among Trump voters, 72 percent say what is most important is reelecting the president, including 47 percent who say this is extremely important, while 21 percent say their motivation is to defeat Biden.

Among Biden voters, the results are roughly the opposite, with 67 percent saying what is most important is defeating the president, including 48 percent who say this is extremely important, and 24 percent saying that electing the former vice president is their main motivation.

National polling results tell only a partial story of the state of the 2020 election. Trump’s hopes for a second term rest on whether he can assemble an electoral college majority in the states, even if he were to lose the popular vote, as he did in 2016. Current polling in battleground states shows a similarly challenging pattern for Trump, however, with the president struggling to replicate the often-narrow victories that led to his election four years ago. Still, the margins in many of those states are closer than the national numbers.

Other polls in recent days have also found Trump trailing by a wide margin nationally, and the president responded Wednesday by shaking up his campaign team, demoting campaign manager Brad Parscale and elevating Bill Stepien to the job of leading the reelection effort. To date, however, the president and his campaign have struggled to settle on a consistent and effective line of attack against Biden.

The poll offers a major reason for that: the pandemic that is weighing heavily on the president. The poll was taken as the number of new cases sets records almost daily and the death toll is rising again. What is not predictable is what the situation will be closer to the election and how any changes might affect judgments of Trump’s handling of the virus and, therefore, his prospects for reelection.

The current standing between the president and his challenger appears closely tied to overall impressions of how Trump is dealing with the country’s major problems. His job approval rating has dropped sharply in the past two months and stands at 39 percent positive and 57 percent negative among voting-age adults, with 48 percent of Americans saying they strongly disapprove of the way he is doing his job. In a late-March poll, when just two points separated Biden and Trump in a head-to-head test, Trump’s approval rating stood at 48 percent positive and 46 percent negative.

The drop in Trump’s overall approval is related to a more precipitous decline in how Americans judge his handling of the coronavirus pandemic. On that question, there has been a net drop of 28 points in his approval margin since March as the president has repeatedly contradicted or ignored health experts in his administration and in the states, stoked confusion about the importance of wearing masks and at times appeared indifferent to the crisis even as conditions in many parts of the country were worsening. Currently, 38 percent approve of Trump’s handling of the pandemic, and 60 percent disapprove.

The president’s one consistent strength over the past few years has been public perceptions of his handling of the economy, especially before the pandemic forced businesses to close and millions of workers to be laid off, sending the unemployment rate soaring into double digits.

Today, despite the country’s economic problems, he is still narrowly in positive territory, with 50 percent of Americans approving of his handling of the economy and 47 percent disapproving. In late March, he enjoyed a far-more positive rating, with 57 percent approving and 38 percent disapproving.

Yet the survey results indicate that voter perceptions of Trump’s handling of the pandemic outweigh perceptions of his handling of the economy in the choice for president.

Among voters who approve of how he has handled the coronavirus, 93 percent support Trump over Biden. But of the far larger group who disapprove of Trump’s handing of the pandemic, an almost equal portion, 89 percent, supports Biden over Trump.

Trump’s level of support among those who approve of his handling of the economy is lower, with 80 percent favoring him over Biden. And Trump also trails Biden by more than 2 to 1 among those adults who say they approve of Trump’s handling of the economy but disapprove of the way he has dealt with the coronavirus.

All told, Biden bests Trump on six of seven attributes and on three of four issues measured in the poll.

Biden is seen as having the better personality and temperament to serve as president by 26 points among adults overall. He is seen as likely to do more to unite the country by 24 points, of better understanding “problems of people like you” by 17 points, as more honest and trustworthy by 14 points, as better representing “your own personal values” by 12 points and as having a better idea of what America should stand for by 10 points. Trump and Biden are even at 45 percent on the question of who is seen as the stronger leader.

Trump’s weakness on the issue of uniting the country shows up in two other questions. In the new poll, 61 percent say the president has done more to divide the country than unite it, and 76 percent say that when Trump talks about people with whom he disagrees, he crosses the line in terms of what’s acceptable, with 21 percent saying he stays within acceptable bounds. Views of Biden are flipped, with 63 percent saying he stays within acceptable bounds and 26 percent saying he crosses the line.

On issues, Biden has a 20-point advantage on who is more trusted to deal with the coronavirus outbreak, a 25-point advantage on race relations and a nine-point advantage on crime and safety.

The second two items are notable because the president and his campaign have embraced a law-and-order message, airing television ads that include clips of urban violence and that portray the former vice president as a captive of left-wing radicals bent on tearing down the country. At a time of heightened racial consciousness, Trump has repeatedly used racist appeals to win support.

Trump’s best issue remains the economy, where 47 percent say they trust him more and 45 percent say they trust Biden more. That represents a drop for Trump from March, when he had an eight-point advantage on economic trust.

Today, 75 percent of adults and 86 percent of registered voters say they are certain to vote in November, the latter figure higher among registered voters than at this point in any of the past three elections. The percentage of adults who back the president and say they are certain to vote stands at 81 percent, similar to the 78 percent noted in May.

Among adults supporting Biden, 77 percent say they are certain to vote, up from 67 percent in May. There has been a bigger jump — from 51 percent to 75 percent — of Biden supporters under age 40 who say they are certain to vote.

Biden’s advantage in the head-to-head matchup against Trump shrinks when only those who say they are certain to vote are analyzed and also when only those who say they voted in 2016 are considered. Among 2016 voters who say they are certain to turn out this year, Biden’s lead shrinks to seven points (53 percent to 46 percent).

The Post-ABC poll finds Trump’s recent decline in support is concentrated in states that have averaged at least 30 daily coronavirus cases per 100,000 residents over the past week, a group that includes Florida, Texas, Arizona and Georgia. Trump led by double digits among voters in these states in May, but the latest survey shows Biden with a slight advantage.

When compared with his performance in 2016, the president has lost ground among several key groups of supporters.

The most significant could be Americans over age 65, a group Trump won by seven points, according to network exit polls, but among whom he now narrowly trails Biden, 51 percent to 46 percent. That, however, is better than the 10-point deficit among seniors in a Post-ABC poll conducted in May.

He also has lost ground among white women. In 2016, he won white women by nine points and today is at risk of losing the group, with 46 percent to Biden’s 50 percent.

Biden holds a lead of 28 points among registered voters under age 40 — larger than the 16-point margin by which Hillary Clinton won that group in 2016. But these younger Biden supporters are much less enthusiastic about Biden. Sixty-seven percent of adults under age 40 who support Biden say they are enthusiastic about him, with 17 percent “very” enthusiastic. Among Biden backers over age 65, 91 percent say they are enthusiastic in their support and 61 percent say they are very enthusiastic.

Overall, Biden leads among all female voters by 60 percent to 35 percent and also among all men by a statistically insignificant 49 percent to 45 percent. Continuing a pattern, white voters split sharply along educational lines, with voters holding four-year college degrees clearly favoring Biden and those without degrees backing Trump, by similar margins.

About 2 in 3 voters in urban areas back Biden, while not-quite 6 in 10 of those in rural areas back the president. In suburban areas, considered the key battleground this fall, a bare majority currently back Biden.

The coronavirus pandemic has spurred demands for voting options in November, but the poll finds that most Americans say they prefer to vote in person rather than by mail, by 59 percent to 38 percent.

Trump has repeatedly attacked voting by mail as subject to fraud, and the new survey shows that slightly more Americans say they think mail-in voting is vulnerable to significant levels of fraud, with 49 percent agreeing with that statement compared with 43 percent who say there are adequate protections to prevent significant fraud.

But those percentages are driven by Trump’s own party, with 73 percent of Republicans saying mail-in voting is subject to significant levels of fraud and 66 percent of Democrats saying there are adequate levels of protection against such problems. The two sides also are divided over how they prefer to vote. A bare majority (51 percent) of Democrats say they prefer to vote by mail this fall, but 54 percent of independents and 79 percent of Republicans say they prefer to vote in person.

The Post-ABC poll was conducted July 12-15 among a random national sample of 1,006 adults, with 75 percent of interviews conducted by cellphone and the remaining 25 percent by landline. The margin of sampling error for overall results is plus or minus 3.5 percentage points; the error margin is four percentage points for the sample of 845 registered voters. Among the 342 Trump supporters, the error margin is six percentage points, and among the 449 Biden supporters, it is five percentage points.

Emily Guskin contributed to this report.