“I would like someone more radical, but because the situation is so dire, I think Joe is our safest bet to beat Trump,” Ms. Devlin said, referring to Mr. Biden. “I used to think that policy was more important, but because of the stinging defeat that we had, I don’t trust that anymore.”

The batch of soak-the-rich proposals draws support well beyond core Democrats, the polling shows. Some Republican strategists say it’s easy to see why: Americans, they say, generally like the idea of taxing other people in order to provide benefits for people like themselves. And they say Ms. Warren’s proposal, which would tax only net worth above $50 million, is narrowly defined enough that most Americans can feel confident they will never pay it. Economists advising Ms. Warren estimate that 75,000 high-wealth American households would owe money to the government under her proposal.

“One of the things that I think is particularly savvy about wealth taxes is, it appeals to people because they don’t think it’s taxing them,” said Mattie Duppler, a conservative political strategist who is a senior fellow at the National Taxpayers Union in Washington.

Kim Mitchell, a 58-year-old Ohio resident, voted for Mr. Trump in 2016. But she is now leaning toward supporting Ms. Warren, largely because of her economic proposals. Wealthy individuals and corporations have too many ways to get out of paying taxes, Ms. Mitchell said. And a country as rich as the United States should be able to ensure its citizens can get health care and a college education without going into debt.

“I’ve always thought of myself as a Republican, but she’s enough to make me jump the fence,” she said of Ms. Warren.

Ms. Mitchell’s father worked for General Electric and retired with a pension. Her husband, now deceased, spent a career in the military. But she is now scraping to get by on a disability check that isn’t keeping up with the cost of living. She said Mr. Trump had failed to deliver on his promise to help people like her improve their lot.

“My husband spent 20 years in the Navy, and I’m living paycheck to paycheck,” she said. “I think the upper 5 or 10 percent are probably succeeding. Us down here in the bottom 10 percent are not.”