Several of the top potential contenders are governors, including Josh Shapiro of Pennsylvania, Gretchen Whitmer of Michigan, Gavin Newsom of California, and Wes Moore of Maryland.
Harris is also being mentioned for a return try at the nomination, as well as former Transportation Secretary Pete Buttigieg.
Trump has teased seeking a third term in office, and even with a constitutional amendment being needed for that to happen, Democrats are saying they want someone who can take on MAGA Republicans.
"I think one of Andrew's strongest qualities is that people feel like he's fighting for them," said Democrat strategist Basil Smikle, a former executive director of the New York State Democratic Party. "And that's the uniqueness of this moment. Candidates can't just sell their good governance. They have to be in the fight, and he proved that during the first Trump administration."