Aides say Mr. Biden has been bracing for weeks for questions about his son onstage at Tuesday’s CNN/New York Times debate. His allies and advisers say that any Democrat who broaches the subject is playing into Mr. Trump’s hands and hurting the party’s cause, and some have suggested Mr. Biden is prepared to make that case if he faces personal attacks, though several of his more prominent opponents have so far been careful to avoid criticizing Mr. Biden’s family.
Still, the national focus on Mr. Biden’s family has become a political vulnerability, some Democrats say, moving him off his campaign message and forcing him to face questions about conflicts of interest.
“It becomes a distraction, and that’s what hurt Hillary Clinton in 2016,” said Bret Nilles, the Democratic Party chairman in Linn County, Iowa, alluding to the scrutiny of Mrs. Clinton’s email practices while she was secretary of state.
The Biden campaign’s strategy has been to push back firmly on Mr. Trump’s claims, and to argue that the president is attacking Mr. Biden because he is concerned about running against him in a general election.
“They can also say, for Democrats who are nervous about it, ‘Hunter’s taken a step to say he won’t be on these boards if the vice president is elected president,’ and they could say, ‘we’ve addressed it and it’s time to move on,’” said Jennifer Palmieri, who was Mrs. Clinton’s communications director in the 2016 presidential campaign. “There are these campaign rituals you have to go through when your campaign does hit a perilous patch like this in order to signal to the press you’re handling it right, and to reassure supporters.”
At a union gathering here on Sunday, Mr. Biden began his remarks by praising Mayor Pete Buttigieg of South Bend, Ind., for a morning television appearance where he defended “me and my family against these outrageous, lying ads” from Mr. Trump. His campaign didn’t respond to several follow-up questions about the younger Mr. Biden’s decision, including about why Hunter Biden didn’t recuse himself earlier.
The last few weeks have been a challenging time for Mr. Biden, aides and allies have said. The Biden family, which is close-knit, has endured painful losses over the years, including the death in 2015 of Mr. Biden’s elder son Beau Biden; Hunter Biden is the former vice president’s only surviving son.