Frederick Westbrook, a retired Las Vegas hotel worker, voted for President Biden in 2020 — as a vote to get Donald J. Trump out of office. He now calls that “the biggest mistake of my life.”

“As a Black man in America, I felt he was doing unjust things,” he said of Mr. Trump. “He’s got a big mouth, he’s not a nice person.” None of that, in his view, has changed. But one thing has.

“Everything is just about the economy,” said Mr. Westbrook, who has started driving for Lyft to support himself on a fixed income in retirement. “I don’t really trust Donald Trump at all. I just think housing, food, my car, my insurance, every single piece of living has gone up.”

In a recent set of polls, Mr. Trump led Mr. Biden in five of six key battleground states, including Nevada. Across the states, Mr. Biden does not have the support of 14 percent of the respondents who said they voted for him in 2020 — voters like Mr. Westbrook who now say they will support Mr. Trump or a third-party candidate, or are undecided or won’t vote.

In follow-up interviews, many poll respondents were engaged on certain issues, and said those that Democrats are strongest on, like abortion rights and preserving democracy, were also important to them. They disliked Mr. Trump’s personality — a reason many voted against him in 2020 — and weren’t necessarily set on their vote.

But other issues had come to the fore and made them unhappy with how things were going — particularly inflation, immigration and foreign policy.

Altogether, the defectors account for just 6 percent of registered voters in Arizona, Georgia, Michigan, Nevada, Pennsylvania and Wisconsin, according to the new surveys by The New York Times, The Philadelphia Inquirer and Siena College. But they could play a decisive role.

They include Democrats, Republicans and independents who voted for Mr. Biden in 2020. Many still support Democrats for Senate, suggesting that Mr. Biden still has a chance to regain support from some of them.

Jaredd Johnson, 25, who works in marketing in Atlanta, said he supported Mr. Biden in 2020 because he hoped he would return the country to a prepandemic normal, but he doesn’t think he has. Though Mr. Johnson has reservations about Mr. Trump, he plans to vote for him.

He said he worries that priorities abroad are distracting from those at home. In conversations with friends and family, he said, they understand the importance of supporting Ukraine and Israel, sending aid to Gaza and helping immigrants.

But, he said, “Our conversations are suddenly less about what’s happening overseas and more about how we are struggling here, too.”

Biden defectors are likelier than others who voted for Mr. Biden in 2020 to say the economy is poor and to want fundamental change to the way things work. They more often are young or Hispanic — groups that have historically voted for Democrats in large numbers, but are to some degree moving toward Republicans. (There are not major differences in the education level of voters who are sticking with Mr. Biden and those who aren’t.)

The surveys found fewer voters moving in the other direction: There were less than half as many Trump defectors in the swing states as there were Biden defectors.

Biden defectors don’t necessarily like Trump

Christopher Sheffield, 61, a counselor for veterans in Thomasville, Ga., said Mr. Trump’s attitudes about race bothered him, but not as much as his concern that conflicts abroad could devolve into a world war.

“I’m an African American — of course I worry about racism,” he said. “But guess what? I’ve been dealing with that my whole life.”

Mr. Biden is “a good guy,” Mr. Sheffield said. “But when I look at him, he looks weak. With North Korea, Putin, and all those boys ready to act, I think they will be a little bit more reluctant to challenge Trump than they would with Biden.” He plans to vote for Mr. Trump.

They’re unhappy with the economy

Though the economy is strong by many traditional measures, half of all registered voters in the surveys said it was poor — including nearly three-quarters of Biden defectors. By comparison, just one in six of those who plan to vote for Mr. Biden again rated the economy as poor.

In interviews, the Biden defectors repeatedly brought up prices. Inflation is still lingering at 3.4 percent, although it has slowed significantly since its 2022 high (9 percent).

Virginia Faris, 54, who lives in Wisconsin, is very satisfied with how things are going for her. But her four young adult children are struggling financially. She blames “Biden’s policies of overspending and printing money,” and plans to vote for Mr. Trump. She said, though, there’s a small chance she’ll change her mind, depending on how the election plays out. (Wisconsin was the only swing state in the poll in which Mr. Biden led among registered voters. Among likely voters, Mr. Biden led only in Michigan.)

They want major changes

Biden defectors were more likely than Biden supporters to say the country needs big, fundamental change. Nearly six in 10 defectors believe that, while a similar share of Biden loyalists say they want to return politics to normal.

“All of our core values are gone, gone, and I’m just not pleased at all,” said Amelia Earwood, 47, a safety trainer at the U.S. Postal Service in Georgia.

She believes the American political and economic systems need to be torn down. Her list of dissatisfactions is long: inflation, illegal immigration, the Biden administration’s recent delay of an arms shipment to Israel.

She called Mr. Trump “a horrible human being,” but added, “I’m voting on his policies, and I think that he could straighten this country out, while Biden made a ginormous mess out of it.”

Some support neither Trump nor Biden

Like Ms. Earwood, most Biden defectors said they weren’t thrilled with either candidate.

Joseph Drobena, 63, a field engineer and a veteran living in Salem, Wis., voted for Mr. Biden in 2020 because he thought that Mr. Trump was too friendly toward President Vladimir V. Putin of Russia, and he was unsure about Mr. Trump’s involvement in Russian interference in the 2016 election.

He’s still worried about that, but said he was “supporting Trump grudgingly,” because he does not like how the Biden administration has handled domestic concerns, including crime and homelessness.

Then again, he doesn’t think Mr. Trump is strong on social policy, either. As he discussed his views, he said his support for Mr. Trump was wavering, and he would consider voting forthe independent candidate Robert F. Kennedy Jr. if he had enough support to be a viable contender.

“We have to do better than one of these two,” he said.