The coronavirus pandemic, a severe economic downturn and the widespread demonstrations in the aftermath of the death of George Floyd in police custody would pose a serious political challenge to any president seeking re-election. They are certainly posing one to President Trump.

His approval rating has fallen to negative 12.7 percentage points among registered or likely voters, down from negative 6.7 points on April 15, according to FiveThirtyEight estimates. And now a wave of new polls shows Joe Biden with a significant national lead, placing him in a stronger position to oust an incumbent president than any challenger since Bill Clinton in the summer of 1992.

The erosion has been fairly broad, spanning virtually all demographic groups. But in a longer-term context, the president’s weakness is most stark in one respect: his deficit among women.

Women were supposed to carry the first female major-party nominee to victory four years ago, as many assumed that Mr. Trump’s treatment of women, including allegations of sexual assault, would prove to be his undoing. But women might be his undoing this time. He trails Mr. Biden by 25 points among them, far worse than his 14-point deficit four years ago. He still leads among men by six points in the most recent polls, about the same margin as he led by in the final polls of registered voters in 2016.

Over the shorter term, the decline in the president’s standing has been particularly pronounced among white voters without a college degree, helping to explain why the Trump campaign has felt compelled to air advertisements in Ohio and Iowa, two mostly white working-class battleground states where Mr. Trump won by nearly 10 points four years ago.

In the most recent polls, white voters without a college degree back the president by 21 points, down from 31 points in March and April and down from the 29-point lead Mr. Trump held in the final polls of registered voters in 2016.

Mr. Trump didn’t just lose support to the undecided column; Mr. Biden ticked up to an average of 37 percent among white voters without a degree. The figure would be enough to assure Mr. Biden the presidency, given his considerable strength among white college graduates. In the most recent polls, white college graduates back Mr. Biden by a 20-point margin, up four points since the spring. It’s also an eight-point improvement for the Democratic nominee since 2016, and a 26-point improvement since 2012.

Mr. Biden has also made some progress toward redressing his weakness among younger voters. Voters ages 18 to 34 now back Mr. Biden by a 22-point margin, up six points from the spring and now somewhat ahead of Hillary Clinton’s lead in the final polls of 2016. Young voters will probably never be a strength for Mr. Biden — a septuagenarian who promised a return to normal, rather than fundamental change during the Democratic primary — but for now his margin is not so small as to constitute a grave threat to his prospects.

Remarkably, Mr. Biden still leads by seven points among voters 65 and over in the most recent surveys, despite the kind of racial unrest that led many of these voters to support Republican candidates at various points in their lifetimes. It should be noted that Mr. Biden’s lead among older voters is somewhat narrower than it was a few months ago, either reflecting the statistical noise of small sample sizes or reflecting the toll of recent events. Yet it is still a commanding strength for Mr. Biden compared with Mrs. Clinton’s five-point deficit among this group four years ago.

Perhaps more surprising in light of recent events is that Mr. Biden has not made substantial gains with nonwhite voters. He leads among them by 46 points in the most recent polls, up a mere percentage point from the polls conducted in March and April. It’s still behind the 50-point margin held by Mrs. Clinton in the final weeks of the 2016 race. Most pollsters do not break out nonwhite voters in much depth because of the small sample size, making it hard to explore the precise sources of Mr. Biden’s relative weakness. But for now, it seems reasonable to assume that his struggles are most acute among young nonwhite voters and nonwhite men, given the overall national figures.

Of course, five months remain until the presidential election. There is plenty of time for the race to swing in Mr. Trump’s favor, just as it did in the final stretch of the 2016 campaign. Indeed, the 2016 race was characterized by a predictable, mean-reverting oscillation between nearly double-digit leads for Mrs. Clinton — as in August and October — and a tighter race in which Mr. Trump trailed in national polls but remained highly competitive — as in July, September and November.

Mr. Biden’s lead in the polls today is not vastly different from the leads Mrs. Clinton claimed at her peaks after the “Access Hollywood” tape was revealed or when Mr. Trump became embroiled in a feud with a Muslim Gold Star military family.

There are reasons to doubt that the polling this year will again take on the character of a slow-motion, sine-wave roller-coaster ride. Many of the swings toward Mr. Trump were driven at least in part by news and negative coverage about Mrs. Clinton’s emails or her health. Joe Biden’s stay-at-home campaign tends to keep the spotlight focused on Mr. Trump. The Trump campaign has not resolved on a central attack on Mr. Biden. Perhaps as a result, Mr. Trump’s high points in national polls have never been as high as they were in 2016.

Even so, this could be a low point for Mr. Trump. There is certainly cause to doubt whether the protests today, or even the president’s early response to the pandemic, will loom as large for voters in November as they do today. No one can predict what the national political environment will look like in five months; surely, no one would have predicted what has unfolded over the last five. The president’s supporters can still hope that the economy will rapidly recover over the summer and fall, before a hypothesized second wave of coronavirus hits over the late fall or winter.

If the race does revert toward the president, as it did on so many occasions four years ago, he could quickly find himself back within striking distance of squeaking out a narrow win. His relative advantage in the Electoral College compared with the nation as a whole, or possibly among likely voters compared with registered voters, means that he doesn’t need to gain anywhere near 10 points to get back within striking distance of re-election. In the final national polls of registered voters in 2016, Mr. Trump trailed by around an average of five points. It was close enough.

But for now, the president trails by too much for these factors to play a decisive role. If the election were held today, the Electoral College would pose no serious obstacle to Mr. Biden, thanks to his strength compared with Mrs. Clinton among white voters and particularly those without a college degree. He would win even if the polls were exactly as wrong as they were four years ago.