Vice President Harris’ campaign has raised $200 million since she emerged as the likely Democratic presidential nominee last week, an eyepopping haul in her race against President Trump.

The campaign, which announced its latest fundraising total on Sunday, said the bulk of the donations — 66 percent — came from first-time contributors in the 2024 election cycle and were made after President Biden announced his exit from the race and endorsed Ms. Harris.

More than 170,000 volunteers have also signed up to help the Harris campaign with phone banking, canvassing and other get-out-the-vote efforts. Election Day is 100 days away.

“The momentum and energy for Vice President Harris is real — and so are the fundamentals of this race: this election will be very close and decided by a small number of voters in just a few states,” the campaign’s communications director, Michael Tyler, wrote in a memo.

Ms. Harris campaigned in Pittsfield, Massachusetts, on Saturday, drawing hundreds to a fundraiser that had been organized when Mr. Biden was still at the top of the Democratic ticket. The fundraiser had originally been expected to raise $400,000 but ended up bringing in about $1.4 million, according to the campaign.

Ms. Harris quickly coalesced Democratic support after Ms. Biden, whose candidacy fizzled following his disastrous June 27 debate performance against Trump, exited the race.

Ms. Harris at her Saturday fundraiser said she remained the “underdog” in the race but that her campaign was picking up steam.

Future Forward, the largest super PAC in Democratic politics, announced last week it had secured $150 million in commitments over the first 24 hours from donors after Mr. Biden bowed out and endorsed Ms. Harris.

Democratic House and Senate candidates say they also have seen a surge in support since Harris emerged as the party’s likely nominee.