WASHINGTON — Senator Elizabeth Warren raised $24.6 million over the last three months, pairing her steady gain in the polls this summer with the biggest quarterly fund-raising haul so far of her presidential campaign, but she fell just short of the total for her main progressive rival, Senator Bernie Sanders of Vermont.

Sanders, who raised $25.3 million, is all but certain to be the top fund-raiser of the July-through-September period, with Warren coming in second among the Democratic contenders. Their totals represent a remarkable moment in the Democratic money race: It is the first three-month period when two candidates who have sworn off the hallmarks of traditional fund-raising, including exclusive donor events and call time for major contributors, brought in the most money.

They each out-raised candidates such as Mayor Pete Buttigieg of South Bend, Ind., who brought in $19.1 million, and former vice president Joe Biden, who reported a quarterly total of $15.2 million, both of whom have kept exclusive fund-raisers in their arsenals.

Warren’s $9 million fund-raising lead over Biden for the quarter is a major sign of strength for her campaign as a handful of early-state and national polls show her narrowly overtaking him as the leader of a crowded primary contest.

In an e-mail to supporters sent Friday morning, Warren’s campaign manager, Roger Lau, said she received more than 940,000 donations from more than 500,000 people, including 300,000 first-time donors, which indicates considerable growth in her donor base as she rises in the polls. The average contribution, the campaign said, was $26.

“This means our grass-roots movement is in an incredible position,’’ Lau wrote, before cheekily urging Warren’s supporters to celebrate. “Close your eyes and picture Wall Street bankers scowling into their catered breakfast.’’

Warren’s campaign ended the third quarter with $25.7 million in the bank — just $6 million more than the $19.7 million she had on hand at the end of June, even though she raised a significant sum of money during the quarter. Her campaign spends heavily on staffing and travel, and the figures released Friday are a reminder that she will need to continue to raise significant sums to sustain her campaign as she takes on new expenses.

Last week, for example, her campaign said it would be spending at least $10 million on advertising and hiring more staffers in primary states that vote in March.

The fund-raising numbers come on the heels of weeks of good news for Warren. Biden’s own fund-raising figure, which was $6 million less than his haul over the previous three months, was a less-than-stellar sign as his campaign confronts a series of unfounded allegations from President Trump about his family’s activities in Ukraine.

If Warren is emerging as Biden’s chief rival for the Democratic nomination, the third quarter fund-raising totals show it is much too early to count Sanders out, even though he failed to post the kind of polling gains Warren has shown in recent months and has made staffing changes in early states like Iowa and New Hampshire.

Sanders is taking a break from the campaign trail after he had a heart attack last week and had two stents put in. His campaign says, however, that he plans to appear in the Oct. 15 debate in Ohio.

Last month, Sanders’ campaign announced he had more than 1 million individual donors.

His campaign announced last week that his average contribution was about $18, which is a sign of his strength with small-dollar donors. Candidates such as Sanders and Warren prize those because they can return to them again and again.

On Friday, progressive Democrats celebrated the apparent success of the fund-raising strategies of Warren and Sanders.

“Grass-roots fund-raising is a measure of grass-roots support, and it’s no accident that Warren and Sanders are leading the pack,’’ said Stephanie Taylor, the cofounder of the Progressive Change Campaign Committee.

“Progressive politics are winning politics, period. They are clearly the strongest, most electable candidates,’’ Taylor said.

Jess Bidgood can be reached at Jess.Bidgood@globe.com.