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LYNDHURST, New Jersey — Former Vice President Joe Biden questioned the Democratic Party's strategy for targeting middle-class voters, suggesting Sunday that Democrats "haven't spoken enough to the fears and aspirations to the people we come from."

"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 a crowd of 1,200 at a campaign rally here.

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

Former Vice President Joe Biden takes a selfie at a campaign event Sunday for New Jersey Democratic gubernatorial candidate Phil Murphy in Lyndhurst. Mel Evans / AP

Biden took the train from his home in Delaware on Sunday to campaign alongside Phil Murphy, the front-runner to win the Democratic nomination for the New Jersey governor's race on June 6.

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Murphy, who was the U.S. ambassador to Germany during the Obama administration, is ahead of the likely Republican nominee, Lt. Gov. Kim Guadagno, in a head-to-head matchup — 50 percent to 25 percent — in the latest Quinnipiac poll.

Biden chided the "crass and mean-spirited and negative and uncomfortable rhetoric that we've been subject to the last 10 months" and said the "world is going to be looking" to November's election in New Jersey to determine whether the United States would "re-establish or reassert who we are."

Biden also contended that Murphy — as a former ambassador — would have better represented the United States than Trump did at the NATO summit in Brussels, Belgium, last week.

"Imagine if Phil had been the ambassador and he was the one representing us, how fundamentally different the projection of America to the world would have been, because it's a basic value set," Biden said.

But Biden also returned to his criticism of his own party's messaging, suggesting that it should extend its efforts to reach out.

He called Murphy a "walking refutation" that a candidate has to "focus on only the economic issues and reject the progressive issues" or "only focus on the progressive issues and forget the working class."

Nearly all of the afternoon crowd was made up of reliably Democratic voters, but Annette Bortone, a Republican from Lyndhurst, sat in the bleachers and proudly said that she would vote for Murphy despite having voted for current Gov. Chris Christie in 2013 and Trump in November.

"I felt Christie [in 2013] was a strong candidate that made a lot of statements that I liked about education and infrastructure, and everything turned up into a big lie," Bortone said, adding that she thinks other Republicans will join her in switching her party allegiance for this election.

"I would think so — only because of what Christie did to this state," she said.

Before the rally, Murphy's campaign passed out "Stop Trump" shirts to attendees.