Jill Biden in her first solo outing of the 2024 campaign said Monday it was "a little shocking" that a sizeable number of Republicans are still thinking of voting for Donald Trump even after his federal indictment, a subject that her husband has tried to avoid speaking about.

She told Democratic donors that the 2024 election presents a choice between what she described as the "strong, steady leadership" of President Joe Biden and the "chaos and corruption, hatred and division" of "MAGA Republicans".

The first lady, speaking to a small group of Democrats in an apartment on Manhattan's Upper East Side, said she was surprised to see a headline before her flight landed that described a majority of Republicans in a poll saying they were still planning to vote for Trump, who is set to appear in a Florida court on Tuesday.

"They don't care about the indictment. So that's a little shocking, I think," she said.

The first lady, opening a campaign swing on the East and West coasts after a gruelling six-day trip abroad, was at times grim as she referred to Trump's time in office and the stakes for next year's election, saying, "We cannot go back to those dark days."

Though the 2024 election in which Biden is seeking reelection is more than a year away, helping him win a second term is a top priority for the first lady, who is also a community college English professor.

She started a three-day fundraising swing Monday in New York City before flying later that night to California. She is scheduled to hold events in San Francisco and Los Angeles, with most of her time to be spent raking in money at four political events, including two in California's Bay Area, to benefit the president's campaign, the Democratic National Committee and Democratic state party committees.

Biden will also join Gabrielle Giffords at a separate event in Los Angeles to mark 30 years of anti-gun violence work by the Giffords Law Center, a nonprofit led by the former congresswoman. Giffords was shot in the head in 2011 during a constituent event in her Arizona district.

As she was in 2020 and the 2022 campaigns, Jill Biden will be active in the 2024 election cycle, helping the Democratic Party build up its resources and infrastructure while reminding supporters of what's at stake.

That message was stark Monday, when she urged donors to "think about where we were three years ago."

"We know what's in store with the MAGA Republicans. We just know it, right? We know because we've lived it. We've seen it," she said. "We know what it's like to see US policy tweeted out in late-night tweet-storms."

She did not name Trump but referred to his habits of blasting off posts on Twitter that announced policies, insulted foreign leaders and nations and even fired staffers.

The first lady was at times blunt about how she saw the 2024 election but was informal and conversational, pressing her palms together, referencing her career as a teacher and referring to her husband as "Joe".

"As she has been for all her husband's presidential campaigns, she will continue to be a formidable presence on the stump," said Elizabeth Alexander, a senior campaign advisor. "Her warmth and approachability combined with her 30-plus years as a classroom teacher, make her an effective messenger on the campaign trail."

The first lady, who introduces herself simply as "Jill", is widely viewed by the political establishment as one of her husband's strongest assets. Democratic consultants and pollsters say people see her as someone they can relate to, maybe even reminding them of their favourite teacher.

"Some people go to presidential fundraisers because, quote, unquote, it's necessary," said Bob Mulholland, a longtime Democratic campaign strategist. "People go to Jill Biden's fundraisers because they want to hear from her."

"Everybody who meets this woman loves her," added Steve Westly, a Bay Area venture capitalist who helped raise large sums of money for Biden in 2020.

Westly, who is set to host the president at his home later in June, said Jill Biden is the "most genuine, sunny, warmhearted, kind person you're ever going to meet. She just exudes that".

Though the young woman whose future husband told her she would never have to give a political speech has become a seasoned public speaker, she still has an occasional off moment. The first lady was criticised, and then apologised, last year for likening the diversity of Hispanics to the flavour of breakfast tacos, and earlier this year she set off a kerfuffle with an off-hand remark that the losers in the NCAA women's basketball final should come to the White House as well as the winners. That idea was roundly panned and quickly died.

Republican strategist Doug Heye said he hasn't really heard Jill Biden's name come up in conversations on that side of the political aisle.

"First ladies tend not to be capital 'P' political, which is a benefit to them," Heye said. "She's not really in that thought process."

He said presidents' wives generally are liked by independent voters and that political parties should be careful about trying to turn them into targets.

"If you're criticising the first lady, that can backfire," Heye said.

Earlier this year, Jill Biden told AP in an interview that her husband has more he would like to get done for the American people.

"He says he's not done," she said. "He's not finished what he's started. And that's what's important."

The 72-year-old first lady participated in nearly 40 campaign and fundraising events in the fall of 2022 in more than a dozen states for Democratic candidates up and down the ballot. She is nine years younger than the president, who turns 81 in November.