ADAMS, Wis. — Nate Zimdars, a Democratic candidate for the Wisconsin State Assembly, arrived at the V.F.W. lodge here after marching in the local Independence Day parade, ready to meet voters at an annual outdoor chicken cookout called the “Chic Nic.” Although the event was hosted by the local Republican Party, Mr. Zimdars was far from nervous being behind enemy lines. He was eager.The county flipped from blue to red in 2016, Mr. Zimdars noted, which meant it could flip again. Plus, national Democrats had done him a favor — they chose former Vice President Joseph R. Biden Jr. for the top of their ticket.“Biden comes across as someone who’s moderate and has experience on both sides of the aisle,” Mr. Zimdars said. “My close family and friends, who are a little more on the Republican side of the fence, said if Biden became the nominee they would vote for him.”Such persuasion is at the core of Mr. Biden’s campaign strategy, designed to bring together moderates, seniors, working-class voters across races and former supporters of President Trump. The approach has helped him jump out to an early lead in polling, both in national surveys and in swing states like Wisconsin, where Mr. Trump won by less than 23,000 votes in 2016. It has also helped him fend off attacks from Mr. Trump, who has sought to cast Mr. Biden as a radical progressive despite his lengthy career as a moderate lawmaker.But if Mr. Biden hopes to maintain his advantage as November draws near, Wisconsin Democrats like Mr. Zimdars have some advice, akin to the famous medical principle of “do no harm,” or the cautionary words of the hit HBO series “The Wire”: “Keep it boring.”Being politically milquetoast is Mr. Biden’s appeal, they said, driving his ability to attract progressives in Milwaukee, moderates in suburbs like Waukesha and more rural voters in places like Adams County, one of the 22 counties in the state that voted for Mr. Trump after backing President Barack Obama in 2012.They don’t lament that Mr. Biden is not a historic candidate like Mr. Obama or Hillary Clinton, or that he lacks bumper-sticker progressive policies like Senators Elizabeth Warren and Bernie Sanders — they’re grateful for it.After the 2016 election, Mrs. Clinton was lambasted for running a risk-averse campaign that seemed to rely on voters finding Mr. Trump’s conduct inherently repugnant. Four years later, facing a changed electoral landscape, many Wisconsin Democrats think Mr. Biden can win the state with that exact playbook.Mr. Biden is “the perfect candidate for this area at this time,” said Matt Mareno, the chairman of the Waukesha Democratic Party.“Trump’s whole rallying cry was that he was an outsider coming to fix the establishment, and now he is the establishment,” Mr. Mareno said. “We’re seeing more and more college-educated white voters leaving him and we’re seeing more seniors leave him. We’re seeing that coalition just completely dissolved down to the very core base of his support.”Several characteristics inform Mr. Biden’s strategy, including his lengthy career as a bipartisan legislator, Mr. Trump’s panned response to the pandemic, and Mr. Biden’s identity as an older white man, the type of politician easily categorized as “presidential.”There are a range of ways Mr. Biden can build a general election coalition in a battleground state like Wisconsin.He could focus on winning back voters in low-population areas, where Mrs. Clinton suffered big losses in 2016.He could build on recent Democratic efforts to target the college-educated white voters that Mr. Trump has, at times, repelled, particularly in suburban counties like Waukesha, Ozaukee and Washington, where Mrs. Clinton outperformed Mr. Obama but also lost some votes to third-party candidates.Or he could seek to motivate reliable Democratic voters like young people, Black voters and Latino voters in Milwaukee, the Democratic stronghold where voter turnout was down significantly in 2016.Mr. Biden’s advisers say he will seek to both appeal to persuadable voters and motivate the party’s base, mimicking the successful campaign of Senator Tammy Baldwin of Wisconsin, a progressive who won re-election in 2018 by an eye-popping 10 points. Mr. Biden led Mr. Trump by 11 points in Wisconsin in a poll by The New York Times and Siena College last month, and more recent polling from other battleground states like Pennsylvania has been even better for him.Representative Mark Pocan, a Democrat who represents Madison, said Mr. Biden’s campaign had already outpaced Mrs. Clinton’s in terms of investment in and attention to Wisconsin. Mr. Pocan said the Clinton campaign “took the purple state for granted,” citing both a lack of visits and financial support for down-ballot candidates.“Donald Trump came and lied to us, but at least he showed up,” he said, calling the Democrats’ losses in 2016 a “duh moment” for the party. It was Democratic voter drop-off across Wisconsin — not big Republican turnout — that most helped Mr. Trump win there, he said.“When one candidate doesn’t campaign and the other one does, you would expect that you might get the results that we got,” Mr. Pocan said. “But no one will ever make that mistake again.”This does not mean that Mr. Biden has avoided skepticism from core Democratic constituencies like young people and progressive minority voters — the same groups that frequently needled Mrs. Clinton and backed Mr. Biden’s rivals in the primary.In fact, the same polls that show Mr. Biden securely ahead of Mr. Trump also find Mr. Biden with tepid numbers among young people and minority voters. His favorability rating decreased in a recent survey by NBC and The Wall Street Journal, driven by shifts among younger Democrats.At a protest in Milwaukee in support of Black Lives Matter this month, Larissa Gladding, 23, said she viewed voting for Biden as the unfortunate cost of beating Mr. Trump. “It doesn’t even feel like it’s an election about young people or he wants the young vote anymore,” she said, adding that she planned to vote for Mr. Biden anyway.Dominique Tonneas, 24, who was interviewed at a fireworks show in Muskego and who plans to vote for Mr. Trump in November, said Mr. Biden’s age and long career meant he wouldn’t bring a new perspective to the table. She said she planned to vote for Mr. Trump, who is only a few years younger, because she preferred his economic policies.What is already clear: The last several months, which have featured the largest protest movement in American history and a pandemic that continues to kill thousands and upend the country’s social and economic fabric, has forced Mr. Biden and Mr. Trump to adjust the structure, and the message, of their campaigns.Sue Schaetzka, who attended the Chic Nic in Adams, said she voted for Mr. Trump in 2016 and planned to do so again in November. But she said the events of the past few months, and particularly the nation’s response to the coronavirus, had changed the way people in her social circles felt about the president.Ms. Schaetzka was unsure Mr. Trump could win the state again this year, particularly against a Democrat like Mr. Biden.“With everything that’s going on with Covid, I know some people are rethinking,” Ms. Schaetzka said.“People just like Biden more than they like Hillary,” she added. “I don’t know if it’s her past and all that, but they didn’t trust her.”At the protest in Milwaukee, young liberals said they planned to vote for Mr. Biden, but the exact things that help him appeal to people like Ms. Schaetzka are what makes them begrudging, even resentful, supporters.They portrayed Mr. Biden as too moderate ideologically and as a doddering elder personally, a critique that mimics the “Sleepy Joe” moniker Mr. Trump has sought to popularize.Diarelis Rodriguez, who marched in the protest, said she understood the young people who saw Mr. Biden and Mr. Trump as two sides of the same coin.“Biden is part of the problem. He helped with the War on Drugs and doesn’t really understand the issues we need him to,” said Ms. Rodriguez, 18. “The people I talk to don’t want to vote because they don’t want to participate in a corrupt system.”But Ms. Rodriguez still said she planned to vote for Mr. Biden in November, though both she and Ms. Gladding wished he embraced more activist rhetoric on matters of racial equality and defunding the police.There’s a reason he has not. Twenty miles away, leaders of the Waukesha Democratic Party said they recently fielded a phone call from a skeptical voter who said she wanted to vote for Mr. Biden, but she was worried Democrats were becoming hostile to police officers.A volunteer named Scott Prindl called the woman back. Mr. Prindl, 65, said the woman had family in law enforcement and he does also. During the phone call, he explained the Black Lives Matter movement and its goals, as he saw them.“The real Black Lives Matter protests are the ones who are peaceful,” Mr. Prindl, who is white, assured the woman over the phone. “It’s outsiders who are coming in and wreaking havoc,” he said, alluding to the destructive political groups that protesters say turned some of the demonstrations violent.The woman was comforted. She will be voting for Democrats in November, she said, and for Mr. Biden over Mr. Trump.