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In July, as the coronavirus pandemic raged, Joe Biden 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, Biden’s only activity was going to church near his Delaware home.

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 Donald 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 programs and other digital outreach.

That guarded strategy reflects the bet 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 Trump almost gleefully flouts.

Yet as Trump barrels ahead with crowded, risky rallies, some Democrats in battleground states are growing increasingly anxious about the trade-offs 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.

Biden has begun to accelerate the pace of his travel, and this week is one of the busiest he has had in months, with two speeches in Delaware, a trip to Florida and an appearance at a CNN town hall Thursday near his hometown, Scranton, Pa. On Friday he will campaign in Minnesota.

Yet the concern among these Democrats is whether, in closely fought states that may be won on the margins, the Biden campaign is engaging every possible voter with an affirmative case for his candidacy, when the other side simply has more traditional tactics they are willing to use.

“It feels like asymmetric warfare,” said Matt Munsey, the Democratic chair in Northampton County in eastern Pennsylvania, one of the counties Trump narrowly flipped in 2016, referring to Biden’s approach versus Trump’s.

Democrats have no interest in replicating Trump’s rallies, which pose health risks and also turn off voters who are alarmed by the dangers of COVID-19. Biden has been eager to make the race a referendum on Trump and his stewardship of the pandemic, a game plan that polls generally suggest is working.

Now flush with cash, the Biden team is active on the airwaves, and Wednesday announced it would spend more than $65 million on paid advertising in battleground states this week.

“Joe Biden is working to earn every vote with a groundbreaking campaign that meets this moment,” said Andrew Bates, a Biden campaign spokesman. “And he’s doing it in the way he would govern: by putting the well-being of the American families he’d fight for every day in office first.”

In a briefing with reporters earlier this month, Biden’s campaign manager, Jennifer O’Malley Dillon, said the team had more than 2,500 staff members who were “supporting the organizing across our battleground states,” and had made a $100 million “investment” in on-the-ground organizing.

Many party officials say they are confident that Biden’s strategy is both sensible and effective. Local officials in Wisconsin say they are seeing great enthusiasm for Biden and expressed confidence that he would win the state.

Mary Arnold, the Democratic chair in rural Columbia County, said she heard many pleas for Biden to come to Wisconsin a few months ago. But recently, she said, people have been more accepting of Biden’s strategy, including keeping his events small.

“I’m getting this much stronger sense that people respect him for that decision because he doesn’t want to kill people,” she said.

Many of Biden’s allies said they were content to have Biden mostly remain at his house in the summer, not wanting to interrupt what they viewed as Trump’s self-sabotage. Still, in late August, as Trump intensified his “law and order” message and painted Biden as a “Trojan horse” of the liberal left, demands among Democrats to see Biden traveling more and speaking to voters directly reached a fever pitch. Aides in early September previewed a fall strategy that included an escalated travel schedule, a promise the candidate has made good on the last two weeks.