(CNN) Michael Bloomberg invested almost $1 billion into his short-lived presidential campaign. A single Silicon Valley donor fueled a super PAC that tried to rescue Sen. Elizabeth Warren 's bid for the Democratic nomination. Small-dollar donors warmed to former Vice President Joe Biden .

And President Donald Trump and his allies continued to build a massive war chest for the general election.

Here are some key takeaways from February's campaign-finance reports:

Biden starts to find financial footing

Biden raised more than $18 million in February -- twice the amount his campaign had collected the previous month, and the former vice president entered March with a little more than $12 million remaining in his campaign account.

And that was before his sweep of victories coast to coast this month solidified his political comeback. During the CNN-Univision debate earlier this week , Biden indicated that his campaign already had brought in $33 million in the first two weeks of March.

In February, Biden saw his standing among small-dollar donors improve. About 45% of his individual contributions that month came from in amounts of $200 or less, nearly on par with Trump's February performance among small-dollar contributors.

Tapping into donors who can contribute small amounts online will become even more crucial in a fundraising world upended by the coronavirus outbreak and widespread economic uncertainty.

In the face of the outbreak, Biden's campaign has had to pull down in-person fundraising events in Illinois, Delaware and Florida, according to interviews with fundraisers.

With normal campaign functions sidelined, Biden on Friday night held a virtual fundraiser with New Jersey donors -- addressing them from a brown leather couch at his home in Wilmington, Delaware, according to a pool report.

The campaign did not disclose how much was raised at the event, organized by cosmetics company founder Bobbi Brown.

Earlier Friday, the campaign sent an email to supporters offering a possible "video call" with the former vice president to those who chip in online.

Sanders outspent Biden -- by a lot

Vermont Sen. Bernie Sanders raised a massive sum in February -- more than $47 million, according to his campaign's filing Friday with the Federal Election Commission.

And he spent nearly as much: Burning through $45 million -- or more than three times the $13.1 million spent by Biden's camp in February.

Despite the heavy spending, Sanders entered March with a substantial financial cushion of nearly $18.7 million in leftover cash, his filings show.

Sanders said this week he still was assessing the state of his campaign after the string of Biden victories had effectively closed his path to the Democratic presidential nomination.

Trump stockpile

Even as Biden has touted fresh donations, Democrats are up against the well-funded machine of an incumbent president.

The Trump campaign and affiliated committees brought in more than $86 million in February, according to campaign manager Brad Parscale.

And Trump entered the month with $94.4 million remaining in his campaign coffers, according to the filings with the Federal Election Commission.

Bloomberg's billion-dollar bet

The new filings also revealed Bloomberg had invested a staggering $935 million of his personal fortune through February into his bid for the Democratic presidential nomination -- shattering all records for self-funded candidates.

In February alone, the former New York City mayor's campaign reported spending $466 million -- or roughly $16 million a day.

The billionaire left the race this month, a little more than three months after he launched his campaign, having won just a single contest: the tiny US territory of American Samoa

Warren's benefactor revealed

Most of the super PAC money spent to boost Warren's presidential campaign came from a single source: Silicon Valley donor Karla Jurvetson, who provided $14.6 million to the pro-Warren Persist PAC , the filings show.

The group launched in February and quickly ramped up its spending ahead of the Nevada caucuses in an effort to boost the Massachusetts senator as her campaign struggled. In all, the PAC spent more than $13.5 million on advertising to influence the race, according to data compiled by the ad-tracking firm CMAG.

Warren, who made fighting big-money corruption a central tenet of her White House bid, reversed course and declined to disavow super PAC help once Persist PAC began to work on her behalf.

Jurvetson's donation accounted for the vast majority of the $15.1 million the Persist PAC reported collecting in February.

CORRECTION: This story has been updated to correct the month for Sen. Bernie Sanders' fundraising.