Welcome to Poll Watch, our weekly look at polling data and survey research on the candidates, voters and issues that will shape the 2020 election.

If the presidential election were held today, polls in crucial swing states like Florida, Michigan and Pennsylvania suggest that Joseph R. Biden Jr. would be in position for a narrow victory.

The disquieting news for Democrats is that at the same point in 2016, Hillary Clinton was in a better position.

Some Americans have lost faith in President Trump’s handling of the coronavirus crisis, but the country’s deeply entrenched partisan divide has prevented the president from losing more than a few percentage points on his overall approval rating.

Besides, the Electoral College has a meaningful Republican tilt, and those who turn out to vote tend to be slightly more conservative than the general population. Add to that Republicans’ efforts to limit access to voting among predominantly Democratic populations, and Mr. Trump might well become the first president in history to win two full terms without once winning a plurality of the popular vote.

State polls proved problematic during the 2016 presidential race — that much is well known. But with no guarantee that a repeat won’t occur this year, it bears noting that Mrs. Clinton was considerably further ahead of Mr. Trump in many swing state polls in spring 2016 than Mr. Biden is now.

Real Clear Politics polling averages show Mr. Biden leading Mr. Trump in most polls of Florida, Michigan, Pennsylvania and Wisconsin. But on average, the former vice president’s lead in each of those states’ aggregates is only about half what Mrs. Clinton’s was at this point in 2016, six months before she was defeated.

Trump’s ‘golden rule’ applies during the crisis.

So far the golden rule of Mr. Trump’s presidency — that his approval ratings shall not budge more than a few percentage points — has held true throughout the coronavirus pandemic. Since the start of this year, his ratings have wavered but never left the mid- to high 40s.

That carries over into perceptions of how Mr. Trump has dealt with the coronavirus specifically. And, importantly, it holds true in swing states.

A University of New Hampshire poll released this week had encouraging news for Mr. Trump. While his overall virus approval rating in that state remained underwater, independents’ approval jumped in the past month by 21 percentage points, showing that his message — inconsistent though it may be — is still persuasive for some key voters.

Surveys released this week of Florida, Michigan and Pennsylvania found approval of his handling of the pandemic varying from 44 percent to 46 percent of registered voters in those states, reflective of the national average.

In Michigan and Pennsylvania, Biden doesn’t necessarily benefit from people’s support of Democratic governors.

These new state polls show that even in places where Mr. Trump has clashed with popular Democratic governors, Mr. Biden will not be able to lean on support for state-level Democrats in his fight against the president.

In Fox News polls of Michigan and Pennsylvania, well over three in five voters approved of their Democratic governor’s job performance, including large majorities of independents and moderates. But in each case, that was far more than those who said they would vote for Mr. Biden in November.

And voters appear to see their governor as separate from their vote in the presidential election. In a hypothetical matchup against Mr. Trump, Mr. Biden didn’t do markedly better when Michigan voters were asked about a hypothetical ticket that included their governor, Gretchen Whitmer, as his running mate. In each case, 49 percent said they would vote for Mr. Biden over Mr. Trump.

In Florida, Biden emerges from the primary race looking weakened — but with room to grow.

A Quinnipiac University poll of Florida released on Wednesday showed Mr. Biden with a slight edge among registered voters, but that spread of four percentage points was within the margin of error. Mr. Biden has fallen since June, when he led Mr. Trump, 50 percent to 41 percent.

Biden’s victorious campaign for the Democratic nomination has done little to put wind in the former vice president’s sails, but rather has left him in a slightly worse position in a matchup against Mr. Trump than when he began. And with the pandemic keeping Mr. Biden holed up in Delaware, he has struggled to command a bully pulpit since becoming the Democrats’ presumptive nominee.

Mr. Biden’s favorability rating is now just 43 percent among registered voters in Florida, down from 49 percent in a Quinnipiac poll of the state a year ago. His plus-3 net favorability rating there is now within the margin of error. Still, 14 percent of Floridians haven’t made up their mind about him, meaning he has far more room to grow than does Mr. Trump, whose net rating is minus-7.

Hispanic voters play an important role in Florida, and in this demographic Mr. Biden looks anemic. He lost the Hispanic vote to Senator Bernie Sanders in many primaries and caucuses this year, and the new Quinnipiac poll of Florida shows him leading Mr. Trump by just eight percentage points among Hispanic voters, 46 percent to 38 percent. In 2016, both pre-election surveys and exit polls showed Mrs. Clinton leading Mr. Trump by three times as many percentage points among Hispanic voters in Florida.

Among black voters there, too, Mr. Biden shows signs of surprising weakness. Twelve percent said they did not yet know whom they would support, a higher rate of uncertainty than in other demographics.

Young voters remain lukewarm on Biden.

Young people are a demographic in which Mr. Biden badly underperforms compared with most recent Democratic presidential nominees.

In Florida, voters under 35 are actually more likely to see Mr. Biden unfavorably than to hold a positive view of him. But 27 percent say they don’t know enough to feel one way or the other, so he has room to improve.

He leads Mr. Trump by just nine percentage points among Florida voters under 35, a relatively weak edge compared with Mrs. Clinton’s lead of 22 percentage points among this group in a Quinnipiac poll at this point in 2016.

Among millennials in Michigan, Mr. Biden squeaks by with just a 50 percent to 45 percent favorability rating, according to the Fox News poll. He leads Mr. Trump by just eight percentage points among millennials in a head-to-head matchup.

Older voters like Biden, and don’t like Trump’s virus response.

Mr. Biden tends to make up for his relatively weak leads among millennials and Hispanic voters with his strength among those 65 and older. Compared with Mrs. Clinton’s 2016 totals, polls suggest Mr. Biden has made the most gains among the oldest voters.

These voters have largely been unimpressed with Mr. Trump’s handling of the coronavirus crisis, and they will be particularly crucial if Mr. Biden expects to win Florida, which has trended Republican over the past 10 years. Those 65 and over broke for Mr. Trump by 17 percentage points in 2016.

In the Fox polls of Michigan and Pennsylvania, and the Quinnipiac poll of Florida, the oldest voters were consistently the most likely to say that their states should err on the side of keeping their economies closed out of a concern for safety — a stance that Mr. Trump has been reluctant to embrace.

In Florida, Gov. Ron DeSantis, a Republican, resisted calls for weeks to put in place a statewide stay-at-home order, and his handling of the crisis has drawn some of the lowest approval ratings of any governor in the country.