“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…

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.