She reiterated her message at a town-hall-style event in New Hampshire on Thursday. “Our democracy really is on the line,” she said, “and if the only way you can become the Democratic nominee is to be a billionaire or suck up to the billionaires, then look out, America.”

All told, Ms. Warren raised $71 million in 2019 from nearly one million people making more than 2.7 million donations, her campaign said Friday.

When Ms. Warren began her presidential bid a year ago, her fund-raising got off to a slow start. But as the year went on and she gained steam in the primary race, propelled by her seemingly endless stream of policy plans, her grass-roots fund-raising strategy appeared to be paying off. She raised more money in the third quarter than anyone aside from Mr. Sanders, and her fund-raising had grown in each quarter of the year.

Her dip in the fourth quarter — in both fund-raising and polling — came as some of her Democratic rivals attacked her over the critical issue of health care. Ms. Warren had aligned herself with Mr. Sanders in support of a “Medicare for all” single-payer health insurance system, but she faced repeated questions over whether she would raise taxes on the middle class in order to pay for the system and came under sharp criticism at the October debate.

She later released a financing plan that would not raise taxes on the middle class, as well as a plan for transitioning to Medicare for all.

At the beginning of the fourth quarter, in October, national polling showed Ms. Warren as a front-runner in the Democratic race, along with Mr. Biden. She remains in the top tier of candidates, but currently trails both Mr. Biden and Mr. Sanders in national polling averages.

Reid J. Epstein contributed reporting.