MACUNGIE TOWNSHIP, Pa. — President Joe Biden came here Wednesday to a sprawling Mack truck plant in the Lehigh Valley to unveil a plan to pump more federal dollars into American products, like the red, white, and blue trucks lined up behind his lectern.

“Today we’re going to make the biggest enforcement changes in ‘Buy America’ in 70 years,” Biden told about 130 employees, supporters, and elected officials gathered inside the one-million-square-foot facility. The announcement was Biden’s latest attempt to show he’s delivering economic help for everyday workers, one of the major focuses of his first year in office and the issue Democrats hope can help them retain control of Congress in next year’s midterm elections.

Biden’s proposal is to boost American manufacturing by upping the threshold for what products qualify as American “enough” for the federal government to buy.

Currently, the federal government has to spend tax dollars on products made in the United States, but that includes products built with just 55% American components. The new proposal would gradually ramp that up to 75%. Companies would also have to provide proof their products are American-made rather than just sign off that they have met the threshold, Biden said.

“We got a new sheriff in town,” the president said, jacketless, after touring the plant, which builds the cabs, frames, and engines for every Mack truck in North America. “Substantial is gonna mean substantial.”

The increase would be gradual, starting immediately at 60% and rising to 75% by 2029 to allow businesses time to adjust and boost use of American-made parts.

The government spends about $600 billion a year in federal contracts, about half to buy products. That includes about 1,500 Mack trucks used by military and civilian agencies.

The visit came as the Senate appeared to reach a bipartisan agreement on Biden’s infrastructure bill, something he learned about while touring the building. He seemed particularly upbeat, jogging to the lectern for the speech, removing his jacket, and joking at the top of his remarks that he was only there to drive a truck.

Ahead of his visit Republicans said Biden and his policies have hurt manufacturers, blaming the president for rising inflation, businesses’ struggles to find workers, and his decision on his first day in office to block the Keystone XL oil pipeline.

“Every manufacturer needs energy, usually in massive volume, and energy production means jobs,” said Bernadette Comfort, vice chair of the Pennsylvania Republican Party. But Biden’s “anti-energy” policies “are a problem for manufacturers who need reliable and affordable energy,” she said, “and also for families” that rely on the jobs in those industries.

Comfort argued that his latest major proposal, a massive infrastructure program, would only add to the country’s rising inflation.

“On Biden’s watch the money in your pocket and my pocket is worth less and less by the day,” she said. “Now we’re considering more reckless spending. Now’s not the time for that.”

Recent inflation has outstripped wage gains as the economy returns toward normalcy, and June saw the biggest jump in consumer prices in 13 years.

The White House, and many economists, argue that the spike in inflation is temporary and likely to settle down, saying it’s being caused by unique factors around the pandemic. Part of the reason for price increases is that current costs are being measured against prices from last summer, in the midst of the pandemic-enforced economic shutdown. Economists and the Federal Reserve also blame a temporary shortage in supply chains, after months of decreased economic activity, while demand leaps.

But Republicans also point to experts who had warned that Biden’s nearly $2 trillion American Rescue Plan could overheat the economy.

At the plant Wednesday, Biden saw where the huge truck cabs are loaded into frames. He also got a look at a new electric garbage truck as local workers took him around.

The Lehigh Valley is a critical swing region, and outside the warehouse, dozens of supporters of former President Donald Trump lined one side of a street while backers of Biden lined the other. One woman held a “Macungie Welcomes Biden” sign feet away from a man with a “Trump 2020″ flag. At one point, police pushed both groups away from the factory, corralling them into close proximity and leading to some yelling and exchanges of expletives.

This was the second presidential visit in a little over a year to the Allentown area for a talk about manufacturing.

In May 2020, Trump visited the personal protective equipment maker Owens & Minor in Upper Macungie to tout the opportunity for the pandemic to boost American manufacturing through government contracts.

Politically, buying American is a rallying call both parties have tried to claim, as they appeal to union workers and a more broad swath of people in rural and exurban parts of swing states like Pennsylvania where manufacturing and factories once ruled. Today less than 10% of the labor force works in factories.

But the need to boost that became evident during the pandemic, with shortages in PPE and other health and medical equipment.

It’s also an issue in the tech sector, where the United States is heavily dependent on China and Taiwan for micro computer chips used in computers, phones, and Mack truck engines.

Staff writer Joseph N. DiStefano contributed to this article.