Joe Raedle via Getty Images Florida Sen. Marco Rubio's presidential campaign was sustained thanks to seven-figure checks written by billionaires to a super PAC supporting him.

WASHINGTON -- As Donald Trump rolled up early primary and caucus wins, the nation’s Republican billionaires poured money into a super PAC backing the presidential campaign of Sen. Marco Rubio (R-Fla.).

The $25 million provided by the party’s establishment donors to Conservative Solutions PAC in February, however, was futile. Rubio dropped out of the race on March 15 after losing his home state of Florida to Trump.

Among the billionaires and centimillionaires making seven-figure contributions to Rubio’s super PAC in February were hedge fund managers Paul Singer and Ken Griffin, each giving $2.5 million. Poultry magnate Ronald Cameron donated $5 million, as did ex-AIG head Hank Greenberg through two corporations connected to him. Oracle Chairman Lawrence Ellison donated $1 million. So did Rubio’s patron, Miami used-car salesman Norman Braman.

Other $1 million donors included Joplin, Missouri, roofing executive David Humphreys and his sister Sarah Atkins; Besilu Stables LLC, a company owned by Miami businessman Benjamin Leon; and Access Industries, a company owned by billionaire investor Len Blavatnik.

The seven-figure contributions accounted for $21 million of the $25 million total the super PAC received in February.

Other Republican establishment donors seeking to save their party and Rubio’s candidacy included Arizona Diamondbacks owner Earl Kendrick, hedge fund billionaire Seth Klarman, Chicago-based investor David Herro, the DeVos family and Stephens Inc. CEO Warren Stephens.

The group also received a $250,000 contribution from Decor Services LLC. The Delaware company has no known owner. It was founded on Jan. 12 and days later donated $250,000 to a super PAC that supported New Jersey Gov. Chris Christie’s failed Republican presidential bid. Campaign finance watchdog groups Democracy 21 and Campaign Legal Center filed a complaint against Decor Services LLC on March 2 for illegally obscuring the true source of the pro-Christie donation.

Conservative Solutions PAC was one of a trio of super PACs that turned their fire on Trump after he won victories in New Hampshire, Nevada and South Carolina. The pro-Rubio group ultimately spent $4.8 million against Trump, but most of its money -- $38.8 million -- went to promoting Rubio.

Although the source of the group’s March funding will not be disclosed until April 20, Republican donors continued to pour money into the super PAC up until Rubio left the race. Conservative Solutions PAC received another $17 million in March.