Fresh off an overwhelming victory in South Carolina’s Democratic primary, President Biden rallied supporters on Sunday in Nevada, saying that he had kept his promises to the Black and Hispanic voters who helped elect him.

Mr. Biden spoke at a community center in the historic Westside neighborhood of Las Vegas, home to an African American community in a critical battleground state. He rattled off statistics about reductions in child poverty for Black, Hispanic and Indigenous people, talked about growth in minority-owned business and attacked former President Donald J. Trump for saying that immigration was “poisoning the blood” of the United States.

But he seemed to acknowledge that many voters were skeptical of his accomplishments as president at a time when his approval rating had sunk below 40 percent

“I know, we know, we have a lot more to do,” Mr. Biden said. “Not everyone is feeling the benefits of our investments and progress yet.”

The president has been working to shore up his support among Black and Hispanic voters, who make up key Democratic constituencies, as Mr. Trump, his likely Republican opponent in November, tries to make inroads among both groups.

Nevada will hold its Democratic primary on Tuesday, the party’s second official nominating contest after South Carolina. But Mr. Biden faces scant opposition here. One long-shot challenger, Representative Dean Phillips of Minnesota — who finished third in South Carolina on Saturday, behind the self-help author Marianne Williamson — will not even be on the ballot.

Instead, Mr. Biden made his trip on Sunday with an eye to the general election. Although Nevada has voted for Democrats in every presidential election since 2008, including for Mr. Biden in 2020, it remains a swing state with a recently elected Republican governor. In November, a New York Times/Siena poll found that Mr. Biden was trailing Mr. Trump by 10 points in Nevada.

The president’s allies are working to bolster him. A pro-Biden super PAC recently announced it would reserve $250 million in advertising across seven battleground states, including Nevada — a record sum.

Shelby Wiltz, the president’s campaign manager in Nevada, said in a statement that the state’s “diverse communities” had delivered the White House for Mr. Biden.

In his narrow victory in Nevada four years ago, Mr. Biden was greatly helped by the state’s influential unions, which represent workers in the hospitality and casino industries. Many of those workers are Hispanic. Last month in Las Vegas, Mr. Trump said that Mr. Biden had “devastated the Latino community” economically and that Hispanics had been “better off” financially under the Trump administration.

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Mr. Biden last visited Nevada in December, when he announced $8.2 billion in funding for passenger rail projects. He slammed Mr. Trump’s approach to infrastructure, saying that the former president had failed to deliver. The Biden campaign is heavily promoting a bipartisan infrastructure bill that Mr. Biden has championed as a cudgel against Mr. Trump, although it could take years for voters to see the results of such projects.

Artie Blanco, a Democratic National Committee member from Nevada, called Mr. Biden the most “pro-worker president we have seen in generations,” but said he and his campaign needed to “ensure the working class know what he has done.”

As it has become more likely that Mr. Trump will win the Republican nomination, Mr. Biden has swung into campaign mode, holding rallies to trumpet his administration’s record. So far, he has faced few road bumps in the primary election. He won New Hampshire as a write-in candidate last month, and then earned 96 percent of the vote in South Carolina.

On Saturday, Mr. Biden met with Black entertainment industry leaders at a fund-raiser at the Los Angeles mansion of George Lucas, the “Star Wars” filmmaker, before traveling to Las Vegas the next day.

Mr. Biden also took time over the weekend to commemorate the birthdays of his sons, Beau and Hunter.

Before leaving for the West Coast, he visited the site of Beau’s grave in Delaware on Saturday. Beau Biden, born on Feb. 3, died at the age of 46 in 2015.

On Sunday, Mr. Biden brunched with Hunter, who turned 54 on Feb. 4, at a restaurant in Los Angeles. Hunter Biden is facing charges in two federal criminal cases that could go to trial during the thick of the presidential campaign.

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