President Biden challenged his Republican opponents on Thursday in their area of political strength, arguing that he has done a better job of managing the economy than former President Donald J. Trump did and accusing his predecessor’s congressional allies of undercutting working-class Americans.

While Mr. Trump has long made his stewardship of the economy his most salient bragging point, Mr. Biden declared that his “Bidenomics” program had done more to help everyday Americans make a living than what he termed “MAGAnomics” ever did. He framed the argument in terms of the fall’s coming budget battles, but it also represented a preview of next year’s campaign.

“They have a very different vision for America,” Mr. Biden said in a speech at Prince George’s Community College in Largo, Md., just outside the nation’s capital, where he held up a copy of budget plans by House Republicans. “Their plan, MAGAnomics, is more extreme than anything America has ever seen before.”

Mr. Biden trained his criticism on Republicans who are threatening to shut down the federal government if their plans are not enacted. The president accused the Republicans of caring more about the wealthy than the working class, pointing to proposals to cut taxes for high-income households and corporations; wring savings from Social Security, Medicare and Medicaid; and reverse initiatives to lower the cost of insulin and other prescription medicine.

The intensified criticism of Republicans follows months of speeches and other messaging by the president and his team promoting the benefits of Bidenomics, a phrase used by critics that they have chosen to embrace. But the credit-taking has not budged Mr. Biden’s poll numbers, and so White House officials now plan to spend the next few weeks or longer emphasizing the contrast with his opponents.

“House Republicans have understandably been reluctant to tout the MAGAnomics Budget — but the White House is going to spend much of this fall doing it for them,” Anita Dunn, a senior adviser to the president, wrote in a memo released to reporters.

Mr. Biden faces strong political headwinds on the economy. A new poll released on Thursday by USA Today and Suffolk University found that only 22 percent of Americans think the economy is improving while 70 percent think it is getting worse. Asked to volunteer a single word to describe the economy, a majority came up with terms like “horrible,” “terrible,” “crashing,” “shambles,” “chaotic” and “expensive.”

Just 34 percent of Americans approved of Mr. Biden’s handling of the economy and, when asked to choose, more expressed faith in his predecessor to improve the country’s economic health than they did in the incumbent, 47 percent to 36 percent.

Mr. Trump sought to rebut Mr. Biden even before the speech. “The public has not been fooled,” his campaign said in a statement. “They see Bidenomics for what it is: inflation, taxation, submission and failure.”

“With polls confirming that Americans overwhelmingly reject Biden’s effort to whitewash his abysmal economic record,” the statement added, “he will now attempt to reverse his message 180 degrees, ludicrously trying to blame President Trump for the destruction and misery that Joe Biden himself has wrought.”

Mr. Trump has always used superlatives to exaggerate the strength of the economy while he was in office. While he presided over a strong and generally healthy economy, it was not the best in history, as he has often stated, and before the pandemic it was roughly comparable in many ways to the economy of the last few years of his predecessor, President Barack Obama.

During Mr. Trump’s first two years in office, the economy grew an average of 2.5 percent per quarter on an annualized basis, while it grew an average of 3.1 percent per quarter in Mr. Biden’s first two years coming out of the pandemic, according to a comparison by Barron’s. The stock market soared by 21 percent during the early part of Mr. Trump’s tenure compared with 8.5 percent during a comparable period under Mr. Biden.

Unemployment has been roughly similar during the two administrations, at 3.8 percent near a record low, but job growth under Mr. Biden has far surpassed that under Mr. Trump as the economy rebounds from Covid-19 lockdowns. By last spring, monthly job growth had averaged 470,000 since Mr. Biden took office, compared with 180,000 in the start of Mr. Trump’s administration, Barron’s calculated.

Where Mr. Biden has struggled most economically is with inflation, which averaged around 2 percent under Mr. Trump but peaked at 9 percent last year under Mr. Biden before falling to about 3.7 percent now. Inflation has increased the cost of groceries, clothes, household goods and housing, while eating away at rising wages. The federal deficit is also rising sharply, as have interest rates.

Still, the recession many feared has yet to materialize, and many experts now are more optimistic about what they call a soft landing. Mr. Biden argues that his expansive legislative program has positioned the country for the future better than Mr. Trump ever did through new or repaired airports, roads, bridges and other infrastructure; vast investment in the semiconductor industry; ambitious clean energy programs to combat climate change; and initiatives to bring down the cost of prescription drugs.

“America has the strongest economy in the world of all major economics,” Mr. Biden said. “But all they do is attack it. But you notice something? For all the time they spend attacking me and my plan, here’s what they never do — they never talk about what they want to do.” He added: “It’s like they want to keep it a secret. I don’t blame them.”