Former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE questioned Democrats' strategy to win over middle-class voters at a rally Sunday, saying the negativity coming from President Trump's campaign distracted party leaders from focusing on the issues, according to a NBC News report.

"Because of the negative campaign that [President Donald] Trump ran, how much did we hear about that guy making 50,000 bucks on an assembly line, [and] the woman — his wife — making $28,000 as a hostess?" Biden asked.

"They have $78,000, two kids, [are] living in a metropolitan area, and they can hardly make it," Biden added. "When was the last time you heard us talk about those people?"