You mean besides calling battleground state voters racists? Indeed, the New York Times’ Giovanni Russonello writes in their latest Poll Watch installment. While the toplines in polls keep showing Biden with a persistent national lead, Russonello sees dangerous gaps in the demos that Democrats won in their 2018 midterm bonanza.

So far, it’s looking more like 2016 than 2018:

Because the 2018 election was largely seen as a referendum on President Trump, Democratic strategists are looking to carry those gains forward. Indeed, national and swing-state polls continue to show Joseph R. Biden Jr. with a steady lead — particularly in the suburban areas where Democrats made some of their biggest gains in the midterms.

But Mr. Biden may not be able to count on the same level of support that Democratic candidates received in 2018. Some of the groups that swung hardest in Democrats’ direction in 2016 have been slow to warm to Mr. Biden. Compared with an authoritative study of the 2018 midterm electorate released this week by the Pew Research Center, recent polls show the party’s presidential nominee lagging behind the rates at which certain key demographics broke for the Democrats two years ago.

The Pew study provides yet another confirmation about what actually happened in the 2016 election. Democrats won the midterms because they recovered their ability to turn out the vote. Party-switching was minimal; what changed was basically that Hillary Clinton wasn’t on the ballot:

Voters in 2018 who did not vote in 2016 were a small group (about 11% of all 2018 voters) but an important part of why the Democratic Party made gains. Among the 2016 nonvoters who voted in 2018, Democratic House candidates led Republican House candidates by a more than a two-to-one (68% to 29%) margin.

Had Democrats nominated someone with more charisma — and with a better GOTV plan — they likely would have beaten Donald Trump. We’ll get back to that point at the end, though, as Joe Biden’s having some of the same troubles that hampered Clinton and Democrats four years ago. Biden’s falling off the pace in key demos, Russonello writes, which might end up creating the same problem.

First, young voters:

Scott Keeter, a senior survey adviser at Pew who helped assemble the report, noted that people under 30 accounted for more than one-third of 2018 voters who had not cast ballots in 2016. “That’s a fairly striking figure,” he said. “And they were already a good group for Hillary Clinton, but they became even more Democratic in 2018.”

Yet Mr. Biden is not particularly popular among young people: His favorability rating is five points in the negative among likely voters under 35, according to the latest Quinnipiac University poll. Still, young voters appear to be even less fond of Mr. Trump — and uninterested in sitting out another presidential election.

Next, Hispanics, where red alerts are already going out among Democrats:

Mr. Biden is up on Mr. Trump by anywhere from 20 to 32 points among Hispanic voters nationwide, according to recent polls. That is considerably weaker than Mrs. Clinton’s advantage, and far below the Democrats’ wider lead in 2018. …

“There’s all sorts of signals coming from the polling world,” Mr. Keeter said, “that make it hard to know how enthusiastic the Latino vote is for Biden and ultimately how much they’re going to turn out for him.”

Russonello sees suburban voters as a continuing strong point, however:

Among white suburbanites in particular there was still a slight Republican tilt in the midterms, but these voters chose Democratic candidates 47 percent of the time, according to Pew. That was up from the 38 percent who voted for Mrs. Clinton.

This is one area in which Mr. Biden is well positioned to carry the gains of 2018 forward — and even exceed them. An NPR/PBS NewsHour/Marist College poll last month showed Mr. Biden winning in the suburbs by a whopping 25 points. A separate Marist poll this week of Pennsylvania found Mr. Biden leading in the suburbs by 19 points.

Well, maybe Biden was … until riots broke out in cities across the US and continued all summer long. That not only will change the outlook among suburbanites, especially as the unrest expands, it’s likely to impact the turnout models as well, both in the suburbs and in the cities themselves. It’s one thing to be favored by 25% in areas, but if turnout also declines by five points or so, it may end up either being a wash or worse for Biden.

And this brings us back to the point about 2016. Hillary Clinton had a huuuge money advantage and the good fortune of running against a candidate who was easy to personally dislike. She blew those advantages by running a national-messaging campaign rather than doing the retail politicking necessary to generate turnout. Even then, Clinton had at least some parity, as Trump also disdained that kind of GOTV effort, preferring to do rallies to stoke enthusiasm and then use targeted ads to replace the ground game.

This time around, though, Trump and the RNC are investing heavily in that kind of retail politicking, while Biden isn’t investing at all in a ground game. He’s doing nothing but national messaging and occasional bungee visits to places where polling indicates trouble — which is why he’s heading to Minnesota next week, a state he should easily be carrying. If Russonello is correct about Biden’s strength in the suburbs, this state shouldn’t even be on Biden’s limited radar — and yet he’s breaking his bubble to appear here instead of, say, North Carolina, Florida, Georgia, or Arizona.

Russonello’s right that Biden and Democrats should worry. He just is a little off on how much they should worry, and why it matters — and not just in the presidential election.