Does Biden need a higher gear? Some Democrats think so.

In July, as the coronavirus pandemic raged, Joseph R. Biden Jr. made one trip to a battleground state. In August, he again visited just one swing state. And on the second weekend in September, less than eight weeks before Election Day, Mr. Biden’s only activity was going to church near his Delaware home.

Mr. Biden’s restraint has spilled over into his campaign operation, which was late to appoint top leaders in key states and embraced a far more cautious approach to in-person engagement than President Trump, and even some other Democratic candidates. While the Trump campaign says it is knocking on a million doors a week, the Biden team is relying heavily on TV ads and contacting voters largely through phone calls, text messaging and other digital outreach.

That guarded strategy reflects the bet Mr. Biden’s campaign has made for months: that American voters will reward a sober, responsible approach that mirrors the ways the pandemic has upended their own lives, and follows scientific guidance that Mr. Trump almost gleefully defies.

Yet as Mr. Trump barrels ahead with crowded, risky rallies, some Democrats in battleground states are growing increasingly anxious about the trade-offs Mr. Biden has made. With some polls tightening since the beginning of the summer, they are warning him that virtual events may not be enough to excite voters, and urging him to intensify in-person outreach.