In her most extensive public remarks since her election defeat, Kamala Harris said she is inspired by Americans fighting Trump's agenda despite threats to their freedom or livelihood.
"Instead of an administration working to advance America's highest ideals, we are witnessing the wholesale abandonment of those ideals," Ms Harris said a day after Mr Trump reached 100 days in office.
Before Wednesday, she had barely mentioned the president by name since she conceded defeat to him in November.
In a 15-minute speech, she spoke to the anxiety and confusion which have gripped many of her supporters since Mr Trump took office, but discouraged despair.
"They are counting on the notion that if they can make some people afraid, it will have a chilling effect on others," she said.
"But what they have overlooked is that fear is not the only thing that's contagious. Courage is contagious."
Mr Trump went after his former rival in a campaign-style rally on Tuesday marking his 100th day in office, sarcastically calling her a "great border czar" and a "great candidate" as he repeated some of the lines he routinely delivered during the campaign.
Ms Harris cautioned Americans against viewing Mr Trump's administration as merely chaotic, casting it instead as a "high-velocity event" and the culmination of extensive work on the right to remake government.
"A vessel is being used for the swift implementation of an agenda that has been decades in the making," she said. "An agenda to slash public education. An agenda to shrink government and then privatise its services. All while giving tax breaks to the wealthiest among us."
Ms Harris chose a friendly audience for her return to the political arena, addressing the 20th anniversary gala for Emerge America, an organisation which recruits and trains Democratic women to run for office and grew in part from her own run for San Francisco district attorney in the early 2000s.
The former vice president is ramping up her public presence as Democrats nationally search for a path forwards after November's election, in which Republicans also won control of Congress.
While a slate of high-profile Democrats - from governors to businessmen - seek leadership roles within the party, she retains unique influence and would reshape any future race she chooses to enter.
She praised Democrats who have been especially prolific in criticising Mr Trump, name-dropping senators Cory Booker, Chris Van Hollen, Chris Murphy and Bernie Sanders, along with representatives Jasmine Crockett, Maxwell Frost and Alexandria Ocasio-Cortez.
But she did not take a stand in one of her party's central divides, neither calling for mass mobilisation like Illinois Governor JB Pritzker or questioning Democratic positioning on key issues like California Governor Gavin Newsom.
"I'm not here tonight to offer all the answers," she said. "But I am here to say this: You are not alone and we are all in this together."
But she warned that things will probably get worse before they get better.
"The one check, the one balance, the one power that must not fail is the voice of the people," she said.
Ms Harris, a former state attorney general and US senator from California, has not discouraged speculation she might enter the race to replace the term-limited Mr Newsom, himself a potential contender for president. And she has not ruled out another run for the White House.
She did not address her future on Wednesday.
She continues to fundraise, using a joint committee that includes Harris for President, the Democratic National Committee and state Democratic parties. The Harris Victory Fund reported having about 4.5 million dollars (£3.4 million) on hand at the end of March, according to federal records.
Source: LBC.com
