NYT:

Over the last two years, Ms. Harris has systematically constructed a database of donors and email addresses that raised several million dollars for her fellow Democrats, demonstrating an uncommon potency for a first-term senator, according to federal election records and interviews with numerous political strategists. Now, as she makes her own run for president, her digital following serves as a kind of stealth weapon, putting her in perhaps the best position to challenge the small-dollar fund-raising operations of two top rivals, former Representative Beto O’Rourke of Texas and Senator Bernie Sanders of Vermont.