President Joe Biden on Monday celebrates Labor Day in Philadelphia. (Photo: Pool)

(CNN) โ€” President Joe Biden on Monday threw numerous verbal jabs at his predecessor in a Labor Day speech, aiming to use his administrationโ€™s record as a way to undermine the inroads Donald Trump has made into a core part of Bidenโ€™s political coalition.

In a speech to the Sheet Metal Workersโ€™ Local 19 in Philadelphia, Biden put a sharp edge on his economic message, repeatedly referring to Trump as โ€œthe last guyโ€ and โ€œthe guy who held this job before me.โ€

โ€œWeโ€™re turning things around because of you,โ€ Biden said. โ€œWhen the last guy was here, you were shipping jobs to China. Now weโ€™re bringing jobs home from China. When the last guy was here โ€ฆ your pensions were at risk. We helped save millions of pensions with your help. When the last guy was here, he looked at the world from Park Avenue. I look at it from Scranton, Pennsylvania. I look at it from Claymont, Delaware.โ€

Later, he called Trump a โ€œa great real estate builder, the last guy โ€“ who really didnโ€™t build a damn thing.โ€

Bidenโ€™s trip to the City of Brotherly Love, one of his most frequent stops for presidential travel, marked his latest attempt to woo the union members who have made up the backbone of his base for decades. But, while the president is firmly supported by top union leaders and quickly received endorsements from some of the biggest unions upon announcing his reelection run โ€“ including the AFL-CIO, the Service Employees International Union and the International Brotherhood of Electrical Workers โ€“ his standing among rank-and-file members has weakened in recent years and some of those members have been wooed by the former president.

Notably, the United Auto Workers has yet to endorse him in his 2024 run as that union faces its own standoff with the Big Three automakers. A damaging strike looms in less than two weeks and the White House has found itself navigating treacherous waters in encouraging both sides to come to a deal.

Acting Labor Secretary Julie Su told CNNโ€™s Phil Mattingly earlier Monday that the UAW and the nationโ€™s three unionized automakers โ€“ Ford, General Motors and Stellantis โ€“ may be closer to an agreement than it looks at the moment.

โ€œWith UAW, the parties are talking to each other,โ€ Su said, adding, โ€œit always looks like parties are far apart until they are not.โ€

Biden sought to downplay the likelihood of a strike, saying ahead of the event he was โ€œnot worried about a strike until it happens.โ€

โ€œI donโ€™t think itโ€™s going to happen,โ€ Biden said Monday.

While the president has strong support among organized labor, union members across different sectors were angered by Bidenโ€™s decision to help intervene to avoid a potential rail strike at the end of 2022. CNN reported in July that there is a lingering mistrust among union members over concerns the president would intervene to stop other strikes, a perception that senior administration officials told CNN was misguided.

Despite those lingering misgivings, Biden has positioned himself as the โ€œmost pro-union president everโ€ and touts his labor credentials in almost every economic speech he gives. Since taking office, Biden has made repeated and concerted efforts to burnish his labor credentials.

The president on Monday said his administration was โ€œreplacing trickle-down economics with what everyone on Wall Street is referring to these days as Bidenomics, and guess what? Itโ€™s working. Itโ€™s about building the economy from the middle out and the bottom up not the top down.โ€

โ€œThis is not a political statement, itโ€™s an economic statement,โ€ Biden said. โ€œWhen the middle class does well, everyone does well.โ€

He added: โ€œBidenomics is a blue-collar blueprint for America. Itโ€™s for you.โ€

On Inauguration Day, one of his first acts as president was to fire the Trump-appointed National Labor Relations Board general counsel Peter Robb, an important signal to unions. A month later, he posted a video on social media expressing support for Amazon workers seeking to unionize in Alabama. Heโ€™s made union support a key priority in multiple State of the Union addresses, and after announcing his 2024 reelection bid, Bidenโ€™s first political stop was to a legislative conference for North Americaโ€™s Building Trades Unions.

And heโ€™s held meetings with organizers, including representatives from Starbucks and Amazon unions in May 2022 and a meeting with young organizers last week at the White House.

Biden has โ€œgiven a signal to workers that heโ€™s on their side and they should have a real piece of the pie and they should have obtained the American Dream that has been so elusive over the last few decades,โ€ said D. Taylor, International President of UNITE HERE, which represents 300,000 workers across the hospitality, manufacturing, transportation, gaming, transportation and other industries.

That support comes at the end of what some have termed โ€œhot labor summerโ€ that has galvanized organized labor across many different industries. The Teamsters union ratified a deal with UPS, securing its key negotiating goals and averting a potentially crippling strike for the US economy. The Hollywood writers and actorsโ€™ strikes also continue as they battle with the studios over how streaming services have upended the business and with AI threatening further destabilization. UAW continues to stand firm in its demands with the major automakers.

According to Gallupโ€™s 2022 Work and Education survey, 71% of Americans approve of labor unions โ€“ up from 64% before the pandemic, and the highest since 1965.

On Monday, Biden walked familiar ground by visiting the state of Pennsylvania. As president he has made more than two dozen visits to the Keystone State, a crucial battleground in the presidential race and the state that pushed him over the 270 electoral vote threshold in 2020, sealing his White House win.

Since coming into the White House, the frequent trips to Pennsylvania โ€“ an easy travel from the nationโ€™s capital โ€“ have shown just how critical he and his advisers view the state to his reelection run in 2024. It has emerged as central to Bidenโ€™s strategy of selling his accomplishments to the types of voters heโ€™ll need in order to earn a second term.