Sunday was the single biggest day for online Democratic donations in years — a significant show of enthusiasm after weeks of sluggish fund-raising.

Democrats greeted President Biden’s departure from the presidential race with an avalanche of cash, donating more than $50 million online on Sunday and making it the single biggest day for online Democratic contributions since the 2020 election — with hours to go.

The huge amount is based on a New York Times analysis of the online ticker of contributions maintained by ActBlue, the leading site processing Democratic donations.

With Mr. Biden gone and Vice President Kamala Harris building momentum to claim the nomination, Democrats went online to contribute at a startling pace. Donations spiked from an average of less than $200,000 per hour in the hours before Mr. Biden quit to nearly $11.5 million in a single hour later on Sunday, the analysis shows.